+1 I think it will be a good idea to choose between different rims.
Coleus, I don't get the compatibilty issues you talk off ? If you put a rim that has exactly the same characteristic (width, radius, weight) but a different design/shape, then one rim will not be better than one another.
Of course it would be better if the rims had different characteristics (weight/stamina) so you would have to choose which rim would be more suited to the race you are in (lighter like the RS Watanabe for sprints / heavier but more solid for endurances, etc).
But for now, I would prefer other things to be implemented (such as night and rain, more tracks).