I really don't see where the overlap between them in terms of flavor is. While the Bard and the Beguiler are both 'social' characters and both cast enchantment/illusion spells, the Bard is more of a wandering jack of all trades/buffer, while the Beguiler is more of a trickster/misdirector.

I could see the Beguiler and the Bard teaming up to eat the Spell Thief, giving the spell stealing to bard and the sneak attack type stuff to the Beguiler.

But this is just my personal opinion, and shouldn't be viewed as discouragement. What, in particular, did you think the beguiler did wrong?