It might be possible with an MX-700 or MX-800 since you could program each button to point to a macro which actually played the button and then switched to a different device. The two devices would be the 727 with even parity and the 727 with odd parity. It would be a total pain in the neck to program though.

Another solution would be to find a preprogrammed device in one of the MX series remotes that operates the 727. I don't think my MX-500 has one that is useful, but maybe newer ones have a different code base? Or maybe the 700/800 series could do it with a preprogrammed device?

Perhaps the best solution would be to get one of the new URC remotes, which I believe support the changing parity codes (I can't say for sure. I don't have one - yet). To program the URC remotes, you have to press the key twice on the original remote and when the URC detects that the everything was the same except the parity, it knows you have a device that uses this technique.