The best idea I've come up with is this: The character can bind one Lawful/Chaotic, one Nuetrel, and one Good/Evil at the same time. This would be based on alignment of course, so a Chaotic Good PC (when high enough level to, obviously) could bind one Chaotic type, one Nuetrel type, and one Good type; as where a Lawful Evil PC could bind one Lawful Type, on Neutrel, and one Evil type. True Neutrel characters would be able to choose either or at the time of binding. The bindings would have to be typed for this to work though. Archons would be typed as lawful or good (or both) as where demons would be typed chaotic or evil, demons would be lawful or evil, elementals would be neutral, etc, etc.
It's still completely open though. This class idea has so much potential to work with it feels like I'm trying to bring order to Limbo...
I do like the suggestion of synergies, and if I can find a way to make it work I'll more then likely add it in.
Edit: Also another thing I'm kinda stuck on is should I stick with doing it like I did the Demon Binder with binding specific creatures, or should I just do it by type and have a list of stuff you can choose from based on level?