Short answer: yes, go ahead.
Long answer: yes, with a small “but”.
The “but” is: I am not sure about the role of R1 pull-up. It certainly allows OFF to be driven by an open-collector/drain output or OFF to be floating. I strongly believe this is why it was placed there.
However, it may also serve a secondary function. In absence of any OFF signal, the MOSFET will not turn on until the GS voltage reaches 1–2V (depending on the transistor model), together with GS capacitance and 1MΩ resistor providing a tiny turn-on delay. So it may be shifting powering RFM-0505 until VCC reaches some sensible value. RFM-0505 itself will not be damaged if the voltage is too low (page 1, Note 3), but the output may be out of spec. If you have an oscilloscope, see if there is no weirdness while you power on the entire circuit. I doubt there is, but may be worth spotting the problem now instead of chasing a transient issue later.