Several things:
Pick your Epic Feats first. They come from a shorter list and are more important. NEVER place a normal feat in an epic slot.
Specifically, pick up two Improved Metamagics (shame EK doesn't grant it as a bonus feat, or else you should get three). Also pick up Multispell. Those are the staples of a high-level mage.
For nonepic metamagics: now that all metamagics are at -2 spell level, you should take a look at the more expensive ones.
Quicken goes without saying.
Extend/Persistent is more or less a necessity for a Gish. Check out Wraithstrike from Complete Adventurer.
Twin Spell is pretty good at +2. It is awesome at +1 but alas.
Split Ray is like Twin Spell, though limited to rays. It's only +1 level though, and it stacks with Twin.
Maximize is good at +1.
Admixture is good too, though it's expensive (two feats) and more limited. I'd only pick that up when there are no better choices.
Delay Spell finds use almost solely with Time Stop. If you want to go that way, then there you go.
Non-metamagical caster feats:
Mobile Spellcasting
Extraordinary Spell Aim
Arcane Thesis (pick the spell carefully, though)
On your existing feats:
Improved Critical isn't worth a feat. Just cast Extended Keen Edges on your weapon.
Why did you take EWP? The difference between an Elven Thinblade and a Rapier is an average of 1 damage per strike. Definitely not worth a feat.
Improved Feint isn't worth it. Analyse the Feint mechanic: with I.F. it's a move action. Which means you need a standard action to take advantage. The two together is the same as a full-round action. If you can afford to spend a full-round action pounding away, though, then full-attack is almost always the better choice.
For Shapechange: don't limit youself to forms with Cha-to-Saves. A form that has godly Con and Dex works just as well. Will saves can be shielded against with Mind Blank. Stick to the humanoid forms, though, or your gear won't work.
Two Improved Metamagics were choices right off the bat, actually. One wasn't enough. And I agree about Improved Metamagic not being a EK bonus feat, because a third one would have been nice. Ah well, I'll settle for the prospect of 12th-level spell slots, I suppose. Still gives me a couple of epic feats to look over.
Quicken is back in the build, although I've not updated it yet. Extend/Persistent... wow. I'd never really looked at those before. There's my replacements for Energy Substitution (cold) and Energy Admixture (cold), most likely.
I'll take a close look at Twin and Split Ray -- might come in handy with polar ray for one of my 10+ level spell slots. Maximize is another prospect. Not sure about Delay, but I'll take a look-see at it, just in case.
Mobile Spellcasting might work. Extraordinary Spell Aim is another prospect. I'm not sure Arcane Thesis is worth it, though, in all honesty -- but that's me.
As for chosen feats...
EWP (elven thinblade) is a relic from when I was looking at bladesinger as part of Nethien's build. I kick myself for having discarded it, but I think I wind up better off with Spellsword/Eldritch Knight, so I won't complain. I could stick with rapier instead -- it's not like the damage difference will have much impact, so I'll open it up. Improved Critical was because I hadn't considered Extend Spell at the time -- that will get opened up, too.
Improved Feint was another relic from the original bladesinger design. I figured with what I had in Bluff, maybe I could make use of it, but it's just as well. I'll toss it, too.
I'll probably take Dodge/Mobility to make up for a couple of those open slots. Not sure if Weapon Focus is worth a feat or not, especially since I'm gonna already have a pretty high Dex and have Weapon Finesse for free from Swashbuckler. I won't mess with it for now.
I'll make the tweaks and (hopefully) have the changes up soon.
