Not Another Swashbuckler Build!

[Suteinu]

Well, first off I'll ask, why 4 levels? Most people tend to break off at 3, since 4 doesn't give you anything.
Anyways, Bard is a good choice (my favorite base class) but it would lose some of it's potency with the Swashbuckler multi-classing. Rogue is good if you take Daring Outlaw. Scout with the Riposte acf can be useful and thematic (see if your DM will let it count as SA for the purpose of taking Daring Outlaw). Factotum is quite useful and meshes very well with Swashbuckler.
I'm not too familiar with Savant, but from what I understand it isn't that great compared to Factotum. Beguiler suffers a lot from losing caster levels.

Actually, our house-rule Swashbuckler fix includes Riposte as a regular class feature; a small fix, but along with a base 6 skill points and the Seduction class feature, significant. Especially good w/ Daring Outlaw, to be sure, and the best reason for Rogue levels, but the Factotum is SOOOOOO tempting!

By the by, Waker, cool icon. Reminds me of A Clockwork Orange, but with sharper teeth...