How do you handle combining settings? My group has no interrest at all in the AoR setting, but some may want to play with the force.

But how do you combine them when some players use obligation and others use whatever they use in the force books?

You set the rule in advance for the group. If people are playing Force, you use the Motivator rules for anyone (even Exiles) that play the game. As long as players know what rules are being used in advance, they've got nothing to complain about. If someone is coming into the game wanting to use rules that you are not using, you should either tell them "No", or allow all players a chance to decide if they want to all change to the new rules (and possibly new or converted characters). You should not split the rules or treat some players differently than others.

The system works with multiple systems. You can combine Duty, obligation and Morality in one party. Morality really only works well for force users and should be included for them. Obligation can be combined just fine. Age of Rebellion Core rule book has a page discussing combining Duty with Obligation. And the last Beta update includes guidelines for combining it with Duty and Obligation.

Oh so we just roll for obligation for everyone and then for morality for the force users. that was easy :-)