I can see there is a good argument for the 144,000 being symbolic. Jesus is, after all, not a literal "lamb" and if the 144,000 are a symbolic (spiritual) "Israel of God" then it would made sense that the number is also not literal.
Then again, perhaps the 144,000 is literal, in which case the "Israel" could also be literal. Perhaps there literally are 144,000 chosen ones from Israel. In which case, could the "great crowd" not simply be other anointed Christians above and beyond the 144,000 ?
JWs used to teach that the great crowd also go to heaven. Maybe they will revert back to this as they have done recently on a number of teachings (for example the "new light" on the "generation" being the anointed ones, which was actually "old light" from 1927 ?