i've had this concern and asked the pilot on more than one occasion... response has always been that no APU is not a big deal on the CRJ, because in the case of a flamemout they would air-start anyway (let the wind going thru the engine start it) rather than use the APU to start. That leaves the APU only needed for power and hydros while the engine is out, and the RAT handles it. So nice to have on the ground (so you can start without a huffer cart) but not needed for safe OPS in the air.