I could live with the following changes:
I. Races
1. Removing weapon proficiency/familiarity, stonecunning, combat bonuses and skill bonuses from the nonhuman races and just leaving stat modifiers, skill modifiers and biological abilities (save bonuses, low light vision, etc.)
2. replacing most immunities with +10 save modifiers unless the race is a construct, outsider, etc.
II. Classes
1. More flexability and customizaton
a. a) six generic classes (3 from UA + 3 hybrid classes (expert/warrior, expert/adept, and warrior/adept); or
b) make the classes more customizable by taking a d20Modern approach (but not basing the classes on ability scores)
2. If keeping classes as they currently exist
a) bard: move away from jack of all trades or
b) clerics as spontaneous divine casters (UA) with smaller spell lists determined by deity's domain. Also down the class by reducing the armor proficiency, bab, hit die, two good saves)
c) druid: tone down the class by reducing the armor proficiency, bab, hit die, two good saves);
d) monk: Rewrite for more customization/flexability. As much as I disliked Magic of Incarnum as a whole, I wouldn't mind seeing a monk with an incarnum like mechanic for harnessing ki to produce different effects.
e) Paladin : Replace it with a generic holy warrior class with spells at first level and a bard like spell progression, make them nonspellcasting, or make them PrCs
f) Ranger: rewrite it to start with 0 level spells at first level and spell progress like bard, make them nonspellcasting, or make them PrCs
f) sorcerer: Give a reason to stay 20 levels
-add the common housrule of Eschew Materials at level one and a metamagic feat at levels 5,10,15,20
-add bluff, diplomacy and use magical device as class skills
g) specialist wizards
-use the specialist wizard variant abilities from UA
-specialists get unique spell list as per 1e illusionist
h) include multiple class variants for each class especially the barbarian hunter, cloistered cleric, martial rogue, wilderness rogue, battle sorcerer, urban ranger
III. Combat:
1. Armor as DR
2. the addition of class based defense designed to work with armor
3. reintroduce facing and rear
iv. Magic
1. Spellpoint w/ vitalization (UA) or skill/feat for arcane casters
v Misc.
1. Action Points
2. Favored Environment
3. Weapon Groups instead of the current simple, martial, exotic
4. Saving throws as per d20Modern
5. Less item dependence on magic items
6. Remove +2/+2 skill feats or limit them to first level