5. An “Engineer” class or subclass
Maybe this is the same thing as the Artificer class, I don’t know. But I think of Engineers in a military sense, in charge of mobility, countermobility, and survivability. That’s not exactly what an Artificer does, but there is room for it in the game. For example, an Engineer might open doors, not by picking locks but by using acid or maybe just a crowbar. Maybe he also employs hasty magical obstacles or traps to help the party shape the battlefield. I also think the Engineer class would mix potions or alchemical concoctions for use as magical grenades.
Thinking about Engineers--the would-be Martial Controller build--got me thinking about Warlords and their absence in the D&D Next Playtest materials. Now, WotC has made reference to the idea of bringing the Warlord back in Next, probably as a sub-class of Fighter, and that’s fine. My only point in mentioning it, then, is to note that while I personally like playing Clerics and like having Clerics in my game, the reality is that lots of folks don’t like having to have a Cleric around. The existence of the Warlord class was the first time that I personally thought WotC had developed a viable alternative to the basic Cleric class, and it seemed like a welcome addition to the game’s history and traditions.
7. Lots of heavy thrown weapons
While we’re talking about Warlords, there were a couple of builds in the middle stages of 4e that offered ranged options for the Warlord, generally via heavy thrown weapons. That was a good idea, made better by the existence of a variety of these kinds of weapons--hammers, javelins, nets, bolos, drow throwing knife, etc. I liked all that stuff, even the drow throwing knife. They should bring all of that back.
8. The total absence of “double” weapons, with a few notable exceptions
What I didn’t like was the Star Wars-baiting double-weapons that WotC introduced with one of their early supplements to the core rules. I hated the double sword, double axe, double hammer (!)... all of it. Yuck! I never need to see any of that ever again.
The exceptions to this that I’d allow were the race-specific weapons that had a basis in the lore of the game. For example, the Urgosh, though over-powered, was a decided part of dwarven history. Likewise, the gnome pick-hammer is a thing you see in the books sometimes, and which I would therefore allow in my game.