Archangel would be awesome, but that should be developed on a main team movie, I think.
they could start the X-Force movie with Warren being already Archangel, but that would be such a wasted plot.
Id keep Archangel out, until second movie, in case X-Force is a decent hit. This way, they could use Angel one more time and make him become Archangel thanks to Apocalypse on a main team sequel.
Will Fox make Age of Apocalypse, tho? We'll have to wait and see, as always