Yeah, here's what's going to happen:
Some pimple-faced 19 year old lackey will open your anonymous letter. The instant he sees it is critical of the org., he'll stop reading and pass it up to his boss.
The boss will take the critical letter and immediately, without reading anything of its content, look at the back page to see who signed it, with the idea of forwarding the info to your elders. When he finds no name, he'll immediately throw it in the trash.
Probably about 3 paragraphs of your 10-page letter will actually be read, and and it will be promptly dismissed as the ravings of a disgruntled apostate.
If it makes you feel better to put the words on the paper, go for it. Just don't have any grand expectations of the effect it might have.