I got asked this today, and I didn’t have time to provide a complete answer.

My answer at the time was “a little bit of every edition all rolled into one,” which, I guess is technically right.

But truth be told, my ideal D&D is a Frankengame of about a dozen different sources. Let’s see:

• A MicroLite20/DCC class structure (simple, evocative mechanics without a lot of fiddly bits) with Pathfinder levels of variety. Without the 3.x/PF/4E levels of required CharOp/Build Mastery.
• Backgrounds from 13^th Age instead of set skill lists.
• Backgrounds from D&D Next.
• A cross between D&D Next Expertise Dice and (simple, gridless) combat powers for martial classes.
• Racial Classes from ACKS, expanded to infinity (At least five classes each—a racial-specific variant on Fighter/Cleric/Wizard/Thief/Psion—for every race you can think of; more encouraged).
• OSR-style fast combat.
• 4E-style at-will spells. Because fuck it, it’s a good idea.
• 4E-style Scene Powers (again, simplified).
• 4E-style monster building, with 13^th Age set damages.
• Skill Challenges, done right—like this.
• Morale and Disposition.
• Six tiers: Commoner (DCC-style Funnel), Adventurer (1E-style dungeon delves), Heroic (3.x-style plot-driven play), Paragon (4E-style superheroics), Regency (BECMI-style worldbuilding), and Epic (Deities & Demigods-style re-defining the Cosmos-level shit)
• Meaningful play style changes at each tier.
• Optional add-ons depending on my mood—Weapon Mastery (again, simplified to all get-out), Hirelings, Fate/Luck points.

This is my dream D&D while staying in the realm of what is conventionally called D&D. If we’re moving outside of that:

• Freeform magic from the SAGA System.
• Aspects/Fate Points/Compels.
• Pendragon’s Winter Phase (augmented by the Book of the Manor).
• Social Combat.
• XP tied to Xbox-style achievements.

So there you have it. I hope that answers your question.