You'll find that most modern songs tend to be EXACT whole values of BPM, and don't vary one iota. Part of the whole modern approach to locking everything to the grid, even when it isn't PLAYED that way by tools like Beat Detective in Pro Tools and the like. So, if your MP3 is also locked rigidly to the beat, and you are careful about trimming the start and end points to make it loop nice and tight, I don't see an issue....

Obviously, using audio, your style will HAVE to be played at only the one tempo, at least until more Ketron-like slice and dice techniques become automatic enough to be transparent for the home user, but as long as they BOTH run at the same tempo, you should hear VERY little drift if any at all.

I can 'wild sync' my G70 with a DAW set to the same tempo, and it won't drift noticeably at all for most of the entire song. Definitely not a problem 16 or 32 bars at a time...

Ketron and Lionstracs are on the right path, but you need to have as simple a means of editing those sliced loops as you do the MIDI components of a style for it to be embraced by the arranger community. In the meantime, as long as you are carefull editing your MP3's so that they are tight to a grid (in whole beat values, as arrangers don't do fractional tempos like 123.75 bpm), there's a LOT you can do with a feature like Multipad triggered audio files...

(Wish my Roland had it!)