Simplify what the actual caster can do and increase the functionality of the Summon itself dramatically. The pets skills should make up at least half of your total rotation. Why not just build from the FF11 model and make them a hybrid dps/support class? However I would encourage their supporting skills to be damage oriented as summoner is a dps class in the end. So for instance, Garuda could maybe buff allies in a target AOE (something they don't have on most skills in this game for some reason) that has a chance on each auto attack to reduce the global cooldown (or cast time for casters) of the players next 3 abilities by .5 seconds (probably a bit less for casters) and restore a bit of TP/MP.

Since each pet will have their own exclusive buff and their own mini dps rotation (2-3 skills), you can clip off some of the extraneous skills that SMN has. For instance, you can consolidate Bio/Bio 2 and make up for it with the new pet buffs and dps.