I think it would be a good idea to be able to buy or sell material to other countries. For example; if Russia has investigated T90 tanks and Spain wants to buy several tanks they could make a deal for X number of vehicles, and that the seller sets a price, either in money or resources.
I think it would encourage diplomacy more than to create a coalition, and make the game more entertaining
I think it would encourage diplomacy more than to create a coalition, and make the game more entertaining