One could neutralise the underlying reason for conflict,
i.e. territorial imperative?
By fulfilling the deeper motives for territorial imperative, namely the need for resources and the need for feeling secure, in a manner rendering the need for unilateral possession unneccessary.
By giving members of all groups access to assets in dispute, yet preserving their national identities and securities.
By allotment, for the sake of emphasizing the equality of rights of each group, of an equally sized, undisputed piece of land to each group in the area, irrespective of their relative population sizes (say 400 square kilometers for each group), that could serve as autonomous national headquarters for each group. The remainder of the land around and between these "mini-states" serving as a kind of commonage to which the overflowing populations of each of these member states have equal access for residential and economic purposes and over which each member state has equal constitutional say.
The inclusive area can then contain a confederation of states, governed by (say) a constitution-formulating senate responsible for law and order, with equal representation from each member state. A (lower) House of Representatives responsible for government of the "commonage" can be elected on a non national regional basis.
--- Could a setup of this kind, where each group is by mutual constitutional agreement treated as an entity with equal rights for survival, provide sufficient framework for negotiation toward peaceful co-existence? With, perhaps, external guarantees for confederal integrity, if necessary?