My favourite option would be FE10's anyone-with-anyone supports without conversations, along with a separate, returning Info system, with special conversations available to certain characters in certain support relationships. That way, you can put any two characters together for gameplay purposes, so you don't have to feel like your main team is hindered by your favourite characters' few support options, and it allows for the kind of in-depth conversations that the GBA games and Path of Radiance had.
Actually, this sounds cool.