Given that I, and many others in this thread, use other platforms with this feature in place, I feel fairly confident in saying none of those problems represent a block to doing this. But, in short, most of the contractual relationship is governed by whatever agreements are in place between the creators and Itch need not be involved in those at all.
The only real issue would be that changes to the revenue split and this could function like collaborative bundles do now — everyone has to agree. In that event, all Itch has to do is distribute the funds based on the agreed upon amount. Any other conflict is already remediable under existing contract law and mediation between the parties.