I'm noticing a pattern with suggestions here, which I am guilty of myself, and which I think needs to be stopped. Having lots of suggestions is great, however, the majority of suggestions we're seeing are outlandish.
1. Don't suggest something that's obviously OP. Even if it's elytra-rare, it's OP. New stuff should add extra challenges to the game, not make it easy or make it become the only challenge of the game.
2. Keep it in Mojang's limits. I get grumpy too when Mojang decides arbitrarily to disclude or include things based on what's easiest to code or best for public reputation, but they're right and they make the game.
3. Stay away from the 'too much'. Examples of 'too much' are huge numbers of mobs, suggesting a huge number of things be added, or lots and lots of new colours and coloured blocks. There's only so much you can put in one game.
4. Minecraft has an aesthetic game aspect, but even I have to admit it's primarily a game of function, not form. So when you have an idea, make sure it has more uses than just looking cool or adding to the environment. It should do something for gameplay, even if it's minor.
Again, I'm guilty of some of these things myself, and this is not me telling people what I think they should do. I just think these suggestions would improve the quality of other people's suggestions by keeping them in the spirit of the game, as opposed to feeling like ideas for mods. Quality over quantity, after all.