I wonder if it would be possible to cycle through oscillators, so that each successive gate signal triggered Osc 1, 2, 3, 1, etc. You can get something close to this in Paraphonic mode but you have to hold down the key each time, unless I'm missing something.
This technique can be great for timbral effects and is found on some older synths such as the Korg Mono-Poly I think?