Manbearcat
Legend
In my ideal D&D Next <snip>
In my ideal D&DNext:
1) Martial characters would only have Dailies. When they use them in the shared imaginary space (LOL?), the actual invocation of the player at the table comes forth through the character in the fiction. For instance, player: "I USE DANCE OF THE DEADLY KNIFE GUY AND RUN AROUND 30 FEET SLASHING DUDES IN THEIR BIG DUMB HEADS, OK...I MISSED, LOOKS LIKE THEIR MEET GOES EVERYWHERE! (see 4 and 6 below).
2) Spellcasters would only have at-wills.
3) Come and Get It will now be the default action (like the current Basic Attack) for every class in the game. However, it would only work on Ranged characters that have no melee weapons.
4) You can ONLY deal damage on a miss.
5) Nothing in the game could be proned except oozes.
6) HP would only be meat and every fight would have buzzards and scavengers circling, gorging off the chunks of flesh hacked off left and right. See 4 and 3 above. Shouting at ranged characters and missing with the soundwave is one of the more common ways for this meat to come flying off of characters.
7) Metagame tokens would be rampant. I mean everywhere. And players could have them whenever they want. Player: "Hey GM can I have a metagame token, I just swilled down a tankard of ale and smashed it no the tavern bar and shouted GRARGH!?" GM: "NO BOB...HAVE 5!!!"
8) It would be an open descriptor skill system. However, you could only apply your skills and invoke your metagame tokens to do things that are outrageously in bad faith. If its not bad faith enough, your character has to go on an atonement quest. For instance, Player: "I USE MY ATHLETICS CHECK TO JUMP TO THE MOON AND SPEND MY METAGAME TOKEN TO GRAB IT AND HURL IT AT THE DIRE RAT!" is sufficiently insincere and genre destroying.
9) The magic item system is player-side. However, they can only use it in the most bad-faith, entitled way possible. GM: "There is nothing in that chest". Player: "OH I BEG TO DIFFER THERE GUY. I'M PRETTY SURE THAT CHEST OPENS TO THE EVERFLOWING FOUNTAIN OF LOOT PLANE, NOW THREATENING TO DROWN US IN VORPAL SWORDS AND PEARLS OF POWER AS IT FLOODS THE CHAMBER?"
10) Post-release errata will NOT be performed by WotC until 3 people flood internet message boards with the same gripe, each at least 5 times. But only if these threads are weighed down deeply by edition war rhetoric. No edition war rhetoric and/or you fail to hit the requisite number of repeat posts on the same subject? No changes. Sorry, those are the rules.
I'm sure there are some other things but those are off the top of my head. 5e without any one of them is an absolute dealbreaker.