Forgive me in advance if this has been discussed elsewhere. Is there a way to customize a map so that each player can only deploy armies to a predetermined list of territories? I'm thinking along the lines of how reinforcements are placed in Diplomacy for those of you familiar with it.

Local deployment. Take out bonuses to where you dont want people to deploy.

That may discourage players from conquering territories but it won't stop them from dropping all their reinforcements onto a territory on the far side of the map from any of their other land. Is there a way of designating a specific territory that reinforcements can be placed? Someway of designating a faction's homeland where all armies must mobilize from?

Nope. Nothing even close. The only option is local deployment which only allows for deployment within bonuses.

Best you could do would be to make a map specific for it with capitol cities as independent bonuses and then setup specific templates for it.