While I'm sure there will be some "What if" or "It could happen" type units and perhaps even some buildings of the like, it won't likely be to the extent you'd likely prefer. The problem is that the EB team prefers (to my understanding at least) to give as fair and equal amount of attention to each individual faction as possible. That would mean EVERY faction would need to get a lot of these buildings and units, which would in turn leave far less room for what would otherwise be actual historical buildings and units.