It would qualify as a hack... the only way that gadget would work is:

1) You would need 2 remotes, 1 with this and 1 without. I personally never recommend anything that requires 2 remotes, because it's against the whole purpose of RC.

2) You would somehow have to disable the IR transmitter on the RF remote - by covering the front with black tape, cutting off the IR LED, etc. To note, I'm not completely aware of how the battery pickup systems work, so I would make sure it's able to pick up what it needs purely off the circuit board, and doesn't also require some sort of resonance from the actual LED (in which case snipping it off would be bad).

3) Because of #2, you would not be able to control any other IR devices with the RF remote, except through the RF basestation.