I agree Michael couldn't - and shouldn't! - replace Robin permanently but I'd be very happy for him to replace Emma.
I wouldn't want him to replace Jason though. I know Jason can be very unpleasant but if you ignore the manner in which he expresses himself and focus on the substance, his critique is usually very good. Certainly the celebs who take on board what he says tend to improve, like Donal MacIntyre in series 4. On the other hand, the celebs who take it too personally (hard not to, I know) to the extent that they completely ignore his feedback, tend to plateau and not improve from start to end, like Roxanne and Coleen, also in series 4. While he needs to dial back his style of criticism, I'm not sure if it would be a good thing if he were replaced.
So my vote for next year's panel is Karen, Nicky, Jason, Michael Ball and Robin. (It's just a shame that for some reason they don't want to offer the 5th judge stop to Karen's husband, who's a former British Champion skater and who also coaches.)