The "swap button" system (i.e. the PVP system) works well for classes that have different static combos, like DRG Full Thrust or Chaos Thrust combos... but would break for classes who's combos "fork" or can be "interchanged."

Honestly, this type of system would really help the Duty Finder in general if it were optional. If you give new players the option to implement "dummy buttons" for their basic rotations, while letting veterans/hardcore players customize by keeping everything separate... you would end up with a lot more "good enough" players, and it would not affect the "best of the best" players whatsoever, other than making their DF's a little less aggravating.