I've got some probably-not-so-original musings about why nobody would actually want to "live forever on a paradise Earth." These are the sorts of things that probably make every JW kid (or adult) have some doubts, because the problems are so obvious. The standard JW answer of "It doesn't say in the Bible what will happen, we'll see when we get there" or "wait for the new scrolls to be opened" are totally inadequate because the problems involve the very concept of eternal life in paradise. The WT recommends against "speculation", but this rings hypocritical, since pretty much every publication they've ever printed involves promises and speculation about how great the New World will be. So...
1. What does "perfect human" actually mean? Would we be incapable of making mistakes? Would I never stub my toe, or mispronounce a word, or miss a basketball shot? This question is exemplified by the perennial DC question of "What's one thing you want to do in the paradise?" to which the answer is "I want to learn to play the piano/violin/etc." If we are perfect, wouldn't that imply that we could just observe someone playing an instrument and instantly be able to play it? After all, the time spent learning is, by definition, the time spent making mistakes and eliminating them through practice. If you can't make mistakes, then you learn everything upon first exposure. This problem is reinforced by having perfect memory. If everything you ever read, saw, or heard could be perfectly remembered, learning would be instantaneous. The WT always says that we could never get bored in the new system, because there's so many things to learn and do. But if stuff isn't difficult to do because all mental and physical faculties are without fault, then it seems you could learn everything relatively quickly (especially compared to eternity, where even the most incompetent person could learn everything because he has infinite time to practice). Plus, why do something if it isn't difficult to do? Most adults wouldn't be satisfied playing children's games that are easy to master for even a few minutes. What's the point? I don't see where personal fulfillment would come from. Most people enjoy doing something that challenges them, where they have to work hard to avoid making errors.
Further, is the model of "perfection" one thing? That is, is there basically one type of perfect human, or many types? It seems difficult to imagine more than one type of perfect human, because all the differences that exist between people now are related to their differing mental and physical abilities. Each person is better at some things, and worse at others. If everyone is perfect at everything, where is the distinction? If everyone wants to play the violin, and everyone therefore does learn to play it perfectly, what's so great about you? People's lives are defined in large part by the things they like and devote attention to. But if everyone can be good at everything, where's the variety or uniqueness to be found? In the context of eternity, it seems even worse. After the first billion years, everyone will have pretty much done everything that anyone else has done. Who wants to talk to a bunch of people who already know everything you do, and you know everything they do?
This objection can basically be summed up as the unescapable boredom and uniformity of eternal life as a perfect human surrounded by other perfect humans.
2. Perfection destroys the human experience. Everyday life is full of making mistakes, following whims and impulses, and being helped by or helping other people. If we are perfect, with unerring judgement and unerring abilities, there's no room for any of this. Sure, life would be orderly and rational, which is good, but would it be interesting? Perfect minds and bodies would basically turn humans into superbeings whose experience we couldn't possibly imagine. Perhaps the lives of these superbeings would be great and wonderful beyond what I can contemplate. But why do I care? I'm a human, with human desires, inclinations, and goals. I'm not really enticed by the things that would motivate a perfect superbeing. Just as a dog doesn't care about fine music or scientific knowledge, what reason do I have NOW for wanting to be a superbeing in the future?
Even if I knew I would be a superbeing at some future time, is that superbeing even "me" in any recognizable way? If you take "me" and effectively eliminate all of my distinguishing talents and faults (as explained above) and then also change all of my human desires with those worthy of a "perfect" human, am I even "me" anymore? Who cares about living forever in the future if the person "I" am now won't survive the process of becoming perfect? I could care less if some version of "me" who doesn't share any of my personal qualities survives in the future, no matter how great that future is.
This also touches on the issue of memory of the past in the New System. Would people remember their past life? Would they mourn all the terrible, evil unbelievers who didn't survive to make it to Paradise? It seems like all the survivors would have to be psychopaths not to feel sorry for all those killed (that one infamous Bethel talk about Armageddon seems to confim this) . Also, would we forget our common human heritage, the great cultural, artistic, and intellectual achievements of the past? It seems that according to the WT, all of these things should be hated as part of the "Old System of Things." But is any JW really comfortable with many of the things they hold dear now being destroyed? If you like classical music, would you be fine with all of the great works of the past masters being destroyed because they came from the Old System? If you suddenly became fine with this once the New System arrived, are you really the same person as you were before? If you like famous works of art or literature, or classic cars, or great wine from historic vineyards, do you really want all of that to be destroyed? Again, if the "you" that enters Paradise has no problem with everything Old being wiped out, is it really "you" at all?
3. Everything the WT describes happening in Paradise is mundane and menial. Who wants to live, even with perfect health, as a farmer growing vegetables for eternity? And even if some people would enjoy this, surely not everyone would. Who wants to spend eternity praising God every day and reminding him how great he is? It seems like just an idealized version of feudalism, where the serfs worship the king for the opportunity to cultivate his land. Sure, the serfs are "perfect" in this instance, but they're still just serfs.
Seriously, after cleaning up all the dead bodies, tearing down all the remnants of evil modern society, cleaning up the pollution, petting lions, and building houses for Bible characters, what do JWs actually think they're going to do? If the Paradise is like the Garden of Eden, humans would be returned to a state of ignorance. Will there be philosophers in the New System, or would this be considered a challenge to Gods singular privilege to knowledge of higher things?
What about great acts of engineering? Will JWs live forever as primitive farmers, or will they have to recreate and supercede modern technology, but in a "perfect" way? Will God ever feel threatened by the building projects of perfect humans, like he was by the Tower of Babel? The WT does talk about how JWs will get to learn about all of God's works and rejoice in "spiritual knowledge". But what about humans striving, and exploring, and challenging convention? Won't all of this be destroyed to make them servants only to God's will? Who wants a life that only consists of fulfilling another person's will?
4. The whole live forever/family/sex thing. If everyone lives forever, there can't be new children or the Earth will quickly be over populated. Excluding space colonization (I'll get to that later), there can't be any procreation. And if there isn't any procreation, doesn't that remove one of the defining human experiences, the raising of children? What does it mean to have a mother, a father, or a family if everyone lives forever and no new children are born? Do you ever become a real adult if your parents are always around? Also, because everyone is the same "age", there's nothing to learn from past generations.
And even without children, is there marriage in the New System? What about romantic love and sex? These are core aspects of human existence, and to remove them makes whoever inhabits the Paradise not really human at all. Could you really love one person for eternity, or would that get old pretty fast? If you got new lovers occasionally, wouldn't you eventually run out of people over an eternity? I don't see the JW God making the New System are free-love orgy, though that might make the most sense in this case.
Those are some of my thoughts. If you've got any ideas I'd like to hear them. Also, I'd like to hear any of the crazy speculation about the New System you heard from JWs in the past. I remember:
People will all speak ancient Hebrew
People won't speak at all, but communicate telepathically
People will walk everywhere (like Jesus?) because with an eternity on our hands, there's no reason to get anywhere quickly
People will keep having kids, but humans will continually spread out into the universe and populate other planets
People will come sexless like angels (except apparently the angels that though human women were hot and had sex with them before Noah)
People will be able to fly everywhere / teleportation