A split like what the Angel City mod did to the Korg DW-8000 would be awesome.
The thing is: you would want to have one timbre for the bass and a different one for the chord or lead sound.
The best voice-stealing I've heard (or rather not heard, which is why it's so good), is the Kurzweil K2xxx series one: it steals from the voice which has reached the lowest volume if I'm not mistaken.
Yash