[Agema]

One thing to bear in mind, on the assumption that a player is dead or next to it when their capital falls (not absolutely true, but not far off). It will be reasonably clear who killed who from the VP graph. If people want to avoid this, VPs would not be necessary, it would merely require a player to claim victory in the file - he'll know when he has made it.

With regard to water nations, they might be a good idea. The ease with which various nations can get underwater varies enormously - anyone with easy access to undead or the likes of Agartha with national amphib units can get in quickly, whereas others might not be able to manage it until much later, which could be unbalancing as they'll access all the gold and gems very quickly.