Hi,
is there any fundamental reason for running this as two cells and even considering the complexity of putting a MoM on top? Technically, the most typical reason to use multiple cells (scalability of the IDB) should have vanished with 8.x. There clearly are others (security zoning, deeply separated fiefdoms for certain OSes or even applications in larger environments, support/licensing politics etc), but when they are solvable, the easier solution should be to merge those cells into one. Keep your previous Unix IS and MAs where they are and move everything to the Windows CS on 8.x, attach the clients there and happily have a single point of control for all media and everything else. Just give it a thought.
HTH,
Andre.