that would be a nice change for SC2- instead of building supply, instead create other buildings that generate supply for buildings, of which the buildings that create units keep supply for the units they created-
in other words, your CC generates up to, lets say, 8 supply, just like in SC, but when it is first built, it will keep generating supply, while other buildings created after it will take up the supply that the CC offers.
to keep supply for units, the barrack that creates that unit has a set supply and can create units based on the amount of supply it has.
of course, for a extra boost of supply for units, Depots should still be available.
too make all this simpler, im saying their could be a total of 4 things to handle-
mineral, gas, unit supply, and building supply.
just a thought