I'd adore about six more books about Incarnum. I know not everyone liked it, but it was fantastic for me, personally.
I think it would have been ... interesting... to take the opposite approach from what Wizards did, and make the niche / never-updated classes a little better, instead of a little worse. So, yeah, you can be a Swashbuckler, with cool Swashing and such, but you only get the stuff from the one book.
Instead, they made all the 'secondary' classes just a little worse than core classes, and then supported the ones that caught on (Warlock, Scout... ...uh, Warmage, a little...), keeping them "also-rans". I understand their choice and perspective, and it's the more conservative way to go (...and probably, also, the right one). I just think the alternative would be interesting.
But yeah. More Incarnum. And Psionics. And Bo9S. And, other stuff.
Edit - Yeah, some of the 'supplement' classes were okay-or-better for power. I'm saying in general.