I think it would be kinda cool if they did it like FF8 (words that shall never again be spoken) and you could improve your affinity with each summon; maybe having a team element to it where higher levels of team summoning create more devastating moves. At least, that's what I hoped for when I thought summoning might be a thing that all players had as a limit type move. Guess it could work kinda the same for a Summoner class.