At current market prices, it may not be worth it to make sure that one body *has* to go. The FM does have the advantage of being able to use a real motor drive, instead of the auto winder that was sold for the ELw and EL2.
If you were mulling over keeping an EL or ELw versus an FM, I'd definitely steer you toward the FM, but since the EL2 has pretty much the same electronics as an FE (including a flexible circuit board, instead of the earlier hardwiring), I don't see why you must get rid of one or the other. Pick up a couple 50/2 AI's, put one on the FM, and one on the EL2, then add a MD-12 to the FM. Use them when you feel like shooting either an FM or an EL2.