You can assign the Leslie MFX to any sound, and the standard controls will alter speed. However, most sampled B3’s already have a slow Leslie (or fast in a few cases) already sampled in. So they sound a bit weird and phasey being run through a Leslie a second time!
I’m not too sure about the E80’s soundset, I don’t remember any completely dry G70 drawbar sounds, there were a few on the SRX-07 card, and the BK-9 has a few. Those are about the only ones I liked through the MFX.
An arranger is just a tool. What matters is what you build with it..!