rms detector digital attenuator
Yes, but most analog AGC loops have a very low bandwidth so stability is usually not an issue; I have never had a problem.
A digital attenuator is fine for setting static power levels, or maybe if you are computing the power digitally. However if you are using a RMS detector chip then it seems overly complex to digitize it then control a digital attenuator, when you could use an analog attenuator and op-amp integrator. You can still control the set-point with a digital potentiometer or DAC.
Also, if you are using a true digital feedback loop then you can only move in 1 dB steps over that 32 dB dynamic range. If your feedback loop is continuously twiddling that 1 dB LSB to lock the power it's going to introduce quantization noise which maybe be quite severe depending on the type of signal you are working with You won't have this problem with an analog method. I have never built a digital feedback loop however just off the top of my head it seems like a lot of trouble for an AGC with 32 dB dynamic range (that's about the limit for a single stage analog loop).