It's definitely possible in Creo 2.0. IIRC, in Creo PTC added in assemblies parameter PTC_CONSTRAINT_SET, which you can use to change active constraint set for given component.
So you started with the right idea of making different constraints set for every placement variant, and now in Parametric 2.0 you'd need to just add PTC_CONSTRAINT_SET parameter to the family table and there you could simply change the constraint set's name for the corresponding family instance.