what would be really nice is to have factions that historically went under after a certain date still have advanced units if you managed to pull them through ....

an example for this:
in Medieval 2
- the byzantine should have had a technological nose dive but if the player managed to go over it (and it should be hard) they should have gunpowder units like the others (even if historically they wouldnt be able/around too)

do you know what i mean ?