Mission and Safety Critical RF System
Use wires! Seriously. 

Wireless for pyro control is done, but it is far from trivial and is almost always less reliable then wiring done correctly. 

NASA have some very good reliability briefing documents on how to terminate wiring, how to solder and how to inspect the work for spacecraft applications, well worth tracking down.

It is not so much the radio bit itself as the fact that your radios built in software is now safety and mission critical, and most modules really are not qualified for that kind of use. Consider also that such things as staging never want to be triggerable by a single circuit component failing, you don't want some mosfet suffering a SEU to cause the thing to stage while being fitted to the rail. Everything of that nature should have separate (and monitored!) arm and fire circuitry, interlocked appropriately, and include appropriate error states in the state machines.

Finely stranded flexible wire is your friend together with ample strain relief and joints which are mechanically secure before you solder them (Or, better, crimp them with the right tools, crimp done right is better then solder in high vibration environments).

Also, include monitoring and testing circuitry, if your igniter needs an amp to light off, can you (after the pad is clear) run 1mA thru everything automatically to measure resistance and verify no shorts or opens?

Finally, redundancy does not hurt, you are probably not pushing the limits of the rocket equation and chemical propellant ISP, so two sets of electronics and doubled up igniters, staging and recovery deployment systems are just going to make for a slightly larger motor and not be the mass disaster they would be if at the limits of ISP and mass fraction.

One surprisingly useful radio thing is a simple beacon built with a low phase noise VHF source and AM modulated with simple tone based telemetry. The doppler on the carrier gives you relative velocity and the low frequency am component gives you roll rate if you use a dipole setup such that the rotation of the rocket changes the losses, meanwhile the level of the tones transmits useful things like pressures, temperatures and maybe even strain gauge readings.

A  modern SDR with CP or crossed polarisation aerials can easily give almost real time data from such a thing, and if you have a 4 channel sync sampling setup you can even get bearing without needing to rely on GPS. The nice thing about this is that it degrades more gracefully then a digital transmitter will, your uncertainty values increase as the signal gets weaker, but you can still get something a long way down into the noise where a digital telemetry link will have just stopped working.