Option 1. Sell DND to Green Ronin and put Steve Kenson on as the main designer let him start with 3e or 4e as the basis and take it from there.
Option 2: Take True20 Revised focus a product completely on fantasy, make a couple of small tweaks, and call it D&D
Option 3: Start with 4e
1. Gnomes and Half Orcs replace Dragonborn and Tieflings in PHB1
2. Barbarians, Bards, Druids and Shamans go into the PHB 1
3. Backgrounds are in the PHB 1
4. Bring back skill Points for players
5. Make several skills less broad
6. Remove the +1/2 level bonus from ability checks and skill checks
7. Replace Action Points and Healing Surges with Mutants and Masterminds style Hero Points
8. Saving throws bonuses go back to Con=Fort, Dex=Ref, Wis (or Cha)= Will
9. Paragon Paths and Epic Destinies become optional
10. Divine character class features are based more on the deity's domains
11. Add a Book of Iron Might type system that allows the player to describe martial attacks and gives the DM actual mechanics for determing the difficulty to Push, Pull, Slide
12. Give more concrete benchmarks for p. 42
13. Change the Pantheon
14. Make a few changes to some powers (e.g., CAGI)
14. Come up with some alternatives to some of the Race abilities and class features.
Option 4: Start w/3e
1. Remove level Drain
2. Remove XP costs for spell casting and item creation
3. Use the optional rules from the 3.0 DMG for ability score drain where it is a penalty to hit, skill rolls an saving throws
4. Fewer Absolutes (Sean K Reynolds)
5. Introduce d20 Modern style Occupations/ 4e backgrounds
6. Races
a. Remove the non-biological aspects of race and make them feats similar to 4e
7.Classes
a. tone down the spellcasters (use the bard's spell progression)
b. Smaller lists for clerics based on deity's domains and a few universal spells
c. do away with x/day abilities
d. go to d20Modern or Star Wars talent trees.
e. Possibly fewer classes: Warrior, Rogue, Spellcaster, Warrior/Rogue hybrid, Warrior/Spellcaster hybrid, and Rogue/Spellcaster hybrid
f. Turn Undead, Rage, Sneak Attack, Animal Companion and many other class abilities become feats or talents
g. Skill Points: No class receives less that 4+Int skill points
h. Sample variants (e.g. cloistered cleric, wilderness rogue, martial rogue, urban ranger).
8. Hit Points
a. Remove Hit Points for True20/Mutants and Masterminds Toughness Save
b. Keep Hit points and introduce the Star Wars Conditon track and Unearthed Arcana Death and Dying.
c. Hit Points are static based on Con (Skill can be simulated w/ class defense and feats, Luck can be simulated with Action Points)
9. Saving Throws
a. Change to 4e Defenses
b. A single progression for all classes with a bonus from initial class.
10. Introduce Mutants and Masterminds 2e style Hero Points
11. Introduce Mutants and Masterminds style Complications
12. Base multiclassing on 4e multiclassing.
13. Skills
a. Introduce Unearthed Arcana Extended Skill Checks or 4e Skill Challenges
b. Introduce the Urban/Wilderness skill swaps from the Cityscape web enhancement
14. Feats
a. Replace the unarmed combat feats with those from Brawl, Combat Martial Arts and Defensive Martial Arts feat trees from d20 Modern
b. Do away with the +2/+2 feats
15. Equipment
a. Alchemical Equipment (tanglefoot bags, sunrods, etc ) go to a supplement
b. Spiked Chains, etc. go to a supplemnt
c. Halfling Riding Dogs go to a supplement
d. Bring back more of the real world armor and weapons from previous editons
16. Combat
a. Combat Maneuver system based on Book of Iron Might which allows players to describe what they want to do and gives the DM actual tools to determine difficulty and effects.
b. Rework Grappling
c. Fatigue and Exhaustion from Hit Point Loss
d. Unearthed Arcana Death and Dying
16. Magic
a. All casters are spontaneous casters or go with Psychic's Handbook (Green Ronin) type system
b. Remove alignment based spells
c. Remove absolute spells
d. Remove Target's level/HD from limiting effects of spells. Stage effects on the degree by which the save is missed
e. Alter various spells (e.g. magic missile requires to hit roll)
17. Magic Items
a. Go back into the DMG and under DM control
18, Magic Item Creation: look to Aritifcer's Handbook (Mystic Eye Games)
19. Organize the rules so many of the optional rules and buried rules are more prominent
20. MM1 is based on the AD&D MM1 monster selection with a few additions (Drow, more demon lords, more arch devils)