I wanted late 3.5E, collected and reassembled into a PHB/DMG/MM trio with some whitewashing along the way. Keeping, of course, all the lessons learned from 1e to the MIC, including the fact that DM fiat turns out to blow without good DMs.
Roughly, then, 3.5e modulo Bo9S, MIC item design lessons, divine feats, wild feats. Add in improved monster design (rationalize monster HD, a la "all class levels count the same"). Improve the power balance for summonings/polymorphs without losing the magic (add a summoning level/polymorph level to go along with CR and make long-duration summons/polys more feasible). Smooth some of the mechanics (turn undead, grappling) and voila.
Don't: cheese out and cut/gimp everything hard (like summons/polymorph/magic item economy/NPC design).
I really feel that 3E was too successful, and that the designers forgot all the bad things about 1E/2E that PC/NPC transparency, magic item economy, standardized rule sets etc... helped to fix. Competent DMs that wing the rules, design rule sets that only work if you bend the rules, and so we get Skill Challenge rules where all the advice includes a line amounting to "and then you ignore the skill challenge rules". I don't think the WotC designers ever actually played skill challenges by their rules.
Roughly, then, 3.5e modulo Bo9S, MIC item design lessons, divine feats, wild feats. Add in improved monster design (rationalize monster HD, a la "all class levels count the same"). Improve the power balance for summonings/polymorphs without losing the magic (add a summoning level/polymorph level to go along with CR and make long-duration summons/polys more feasible). Smooth some of the mechanics (turn undead, grappling) and voila.
Don't: cheese out and cut/gimp everything hard (like summons/polymorph/magic item economy/NPC design).
I really feel that 3E was too successful, and that the designers forgot all the bad things about 1E/2E that PC/NPC transparency, magic item economy, standardized rule sets etc... helped to fix. Competent DMs that wing the rules, design rule sets that only work if you bend the rules, and so we get Skill Challenge rules where all the advice includes a line amounting to "and then you ignore the skill challenge rules". I don't think the WotC designers ever actually played skill challenges by their rules.