I agree with a few levels of Rogue being a good idea, for the reasons stated, but mostly for one not stated -- Use Magic Device could give you access to some helpful divine & arcane spells. For instance, if you were able to sneak attack against undead because they'd been hit by a spark of life spell you cast from a scroll or wand, you'd also gain your Insightful Strike bonus because they were now "critical hit vulnerable".
Since you stated you wanted to be a full swashbuckler. I'd recommend a few things:
1) Good call from Feadin on Improved Critical: it will be useless against most undead. Use that feat for something else. Also, why Combat Acrobat? Acrobatic Charge will let you ignore rough terrain at level 7.
2) An item that will let you fly could be really helpful. So could an item that will let you teleport short distances, to get out of trouble when your Spring Attack or basic movement rate won't.
3) Fighters fail Will saves regularly. And it usually is pretty bad when you fail a will save from an undead. Make sure you boost your save as much as possible.
4) Carry a magical bludgeoning weapon as well. Some undead are resistant to piercing, but not to bludgeoning. Or: there's a weapon enhancement that causes a weapon to "count as" meeting all the requirements to overcome a creature's DR for a +2 bonus (Magic Item Compendium, though I don't recall its name right now). I'd say this is probably a must for your weapon.
5) For a feat instead of Improved Critical, I'd recommend Unquenchable Flame of Life from Libris Mortis to boost your saves against supernatural & extraordinary undead abilities. Maybe 2 luck feats, if you were also willing to give up Combat Acrobat.