I’d love this. I’ve actually been emulating this with the one-shot LFO+Fade trick that someone recently posted. I actually managed a pretty convincing 303 emulation last night (minus a tiny bit of the characteristic squelch on the highest resonant peaks) but being able to lock a slide would be SO nice!
Edit: Oh, as a continuation of my experimentation with wave-folder type effects, I did stumble on a very similar effect, and it was done very simply. It was just modulating one ratio between operators, but I can’t remember which algorithm(s) it worked in. It was about as basic a patch as could be though. So I’m not sure adding one specifically would be of much use. I’ll figure out the best sounding algorithm to do this in, and post a few results when I get a chance.