Admittedly, I haven't read Tome of Battle yet, but I have trouble imagining that the swordsage could make the iajutsu master more broken than it already is.
Standard action, 8th level manuver: x4 damage for a single strike if your Concentration check beats their AC (you still have to hit, but, remember, there's nothing saying iaijutsu focus damage isn't multiplied on a crit or in cases like this). There's a lesser one that only deals x2, but, still, Iaijutsu is
all about the first strike.
That said, simple swordsage would be good enough for me.