Changing names middle game = take up 1 more faction slots ; just open your teutonic campaign scripts and faction lists
well that would make it rather pointles, so forget it :D it would be silly to have a ... Yuhezi army owned by Arverni :DDD

@SwissBarbar: point 3 would have to be dependant on faction as some would simply continue fighting( like a strong KH(a weak KH would collapse)) or their Faction would dissolve(like Sweboz) and become rebels. but I agree that It should be more than just an opportunity to loot some expensive buildings when you capture an enemy capital.