1. Less Gamist. Remove the +1/2 to ability checks, change how daily magic items work, allow monsters to get full benefit of magic/equipment bonuses, etc. Reduce the seperation between PCs and NPCs. Change the save system, the duration of some spell effects seem to short.
2. The Skill system: Keep Skill Challenges. Remove the +1/2 to skill checks Go back to 3e skill lists (sans Use Rope) and give more skill points to the 2+ int points per level classes. If necessary, change the cap on how many skills ranks a character can have.
2. The power system. Personally, I would like to see the removal of per encounter and daily abilities (especialy for martial exploits). I'll settle for a way to recharge per encounter as per B09S and dailies via action points.
3. Healing: Put healing powers back with the magical classes. Increase the time of natural healing. Also, less healing surges- maybe limit 1 plus con bonus per day and have them triggered by action points.
Honorable mentions:
- multiclasing: In general, I like the heroic tier multiclassing, but, imo, there should be a way to access the core abiities (the armor and weapons proficiencies or saving throw bonuses) of other classes.
- Equipment: one book bringing back the missing real world armor,weapons and equipment from previous editions.
- (edit) more focus on non-combat activities: classes that are less about combat, more non-combat utilities, etc.
- Magic: bring back illusions, necromancy and summoning (limit to rituals for outsiders and undead legions. For "natural" creatures require they be in the local environment, must be able to get to the character under their own abiity and place a delay) .
- Replace Paladin's divine challenge and the Fighter's Come and Get It. We were told that the designers learned knight's challenge to be a bad idea. In the case of the Paladn's challenge, I don't see how allowing a creature to ignore it by taking damage makes it any better than Knight's Challenge.
- the magic/economy system. Go back to the old monetary types, but move the economy to a silver standard. Then make permanent items more costly to make, more rare and "special" that they become things that motivate characters to seek them out.
- Monsters : Classic monsters in one book. More fluff, more ecology, and more non-combat abilities for monsters (just list the non combat abilities seperately). These things inspire adventures.