Something else that I'd be quite happy to see in 5e
Death of feats. They have become a fiddly little nibbling away at providing corner-case customisation, and if there is a system which gives enough customisations to all classes as it is (as 4e does), then why bother with them?
I know some people love feats, but as this is *my* wishlist, I'd like to see them gone.
I'd rather that "feats" be radically restricted and morphed into non-adventuring abilities that a character might possess but many would not. This would include crafting abilities, language abilities, etc. If you take the "Blacksmith" feat, then you get to use some ability score and/or more general skill to do Blacksmith work. If in doing all that, they want to rename the thing into something better than "feats", fine.
In 3E, "Track" was the good feat, and about the only one they killed. Go figure. "Swim" could let your Athletics ability pertain to swimming. And so on. They didn't like this design because people had to pay a feat to do what many characters should be able to do. But players didn't like that, because there were so many critical things they needed the feats for. Move all that critical stuff into class abilities or some other construct, and keep feats for the less critical things. Then players will be happy to pick the things that matter to them. And if in a given campaign the players want more or less of them, go ahead--it isn't a big balance issue now.
Maybe armor and weapon proficiencies could stay in feats, but I can't think of anything else that affects combat that should be that binary.
So in one sense I agree that "feats" would be removed, but I think there is still a useful design space for, "A character either has this thing or he doesn't. Many don't have it."
In the simple version of the game, every adventurer would be assumed to have a certain preset number of these--the ability to swim, speak an extra language or three, maybe the ability to track. For a more complex character/campaign, you can keep the default list, swap one or two, or go full custom. It's up to you. In this way, "feats" become as much about campaign customization as character tweaking. Want to play a game where everyone plays an instrument in a traveling minstril show? Every character takes "Play Instrument", and the bard PC becomes band leader.
The feat list wouldn't be very long, and would hardly expand at all after the core rules were established. But I see this as a feature, not a bug. Every feat added lowers the value of the previous set, if only slightly. So get a good set and leave it alone.