@Redex Don't know. Considering mags and pets are only visible for others in combat areas, and mags have a different functionality. Also, since everyone can get, level and candy up a pet regardless of being a summoner or not, and changing to the class is free for everyone, I don't see much sense of uniqueness from being the person flinging pets around in a fight.
And then again, mags can be the ultimate monetization thing just by adding more evo devices, both based on collabs and from in game things like for example, more mob and boss themed mags. And while dev work would still be required for models and animations of existing beings from the game, it would be much easier to edit something that's already in game and adapt it for mag use, than making something entirely new.
Or if they want to expand even further, there are SO many things out there Sega can choose to make mags for. Daytona Hornet, After Burner Tomcat, Eggman sitting on his egg mobile, Chibi Space Harrier. really, mags can be anything pretty much. Sega just needs to make it and they will find a group of people who will buy it on a whim.