Yes I think that is the main concern for implementing this. If someone can come up with a good solution then this request is more likely to be implemented.
CDFA wrote:The only issue I really see is that the DT user is going to have to sit in Multi for a long time when the rest of the users finish the map. For long songs, this can turn into a bit of an issue (and I can probably sense a lot of bugs coming from this)
Coincidentally there are similar discussions in another thread: Multiplayer "free play" which is a request for allowing individual players to choose whatever difficulty level within the same mapset. The concern there is that some lower diff maps are considerably shorter than the higher diff so the time gap needs to be addressed. That request, however, has an easy way out which is simply disable the "freedom" if the maps within the mapset are considerably different in length.
I just thought I'll bring it up here cause any potential solution proposed in this thread may work on the other.