I might consider giving them the ability to 'capture' defeated outsiders and summon them via a spell-like ability with limited uses per day, instead of doing it with spells.
Or, considering that certain FF games treated summons as one-off spell effects, just leave the sorcerer 'as-is' and tweak their spell descriptions to resemble summons. For example: Fireball doesn't create a projectile, it opens a portal onto Elemental Fire and an efreet pops out in front of the enemies, then showers them with flame, and vanishes. Admittedly, this doesn't suit all spells. You might want to prepare a special list including some cleric spells, as I recall some summons actually healed the party.
Just my 2gp. This could all be too much bother.