With the Favored Soul, a non-standard class among a number of the of the PHB classes, one thing I've always wanted to see was more use of the 3.5 supplement books for classes and feats. AT the most, I would just kinda run down a number of things I'd always been considering would further enhance the experience.

1. Adaptation of a class or some feats from "The Tome of Battle: The Book of Nine Swords": In a way, the monk plays a lot like a 4ed class considering how some of the powers are designed, but seeing an actual swordsage or warblade as a supplement class would be amazing. With how the power system works in ToB, where the powers work more like spells than actual attack powers, a scaled down list of powers from each of the schools could be used (Like you have for the casters where you don't include the useless-in-combat), and since on the P&P style the powers are designed to be used once per encounter unless recovered, I figured the way to adapt this would be allowing each power a certain number of uses (Like say 2 + level) before the power has to recharge.

2. Drawing in Extra feats from any of the other supplement books. Selfishly, the main one I'm interested in is Versatile Unarmed Strike from PHB2, which allows you to adapt your unarmed attacks to slashing or piercing instead of just being stuck with bludgeoning, something that would be amazingly useful to monks. But there are a number of feats that I find are fairly useful even in a fast paced game like this, like Crossbow Sniper, which would improve use of the crossbow for Rogues who are more focused on trap work to get into melee.

3. Perhaps an expansion of races as well. Although drow and warforged are nice, there are bound to be more abnormal races than that even in Eberron. Hell, maybe add Orcs or Half-orcs, or even Rakshasas if Beelzebub is feeling a bit drafty. Just the thought of more would be better.

Those are my three things at least.