Yeah I agree they should make you choose between Bahamut and Phoenix only to give more control to Phoenix's support capabilities. I really see no reason for the current, rigid cycle of Bahamut to Phoenix anymore unless they just want them to have a fair chance being used at the same amount.

That'll also give us more opportunities to get a 3rd Demi summon in the future, meaning more choices. SMN right now and during Shadowbringers is just too rigid.