Very cool idea.
I'm sure this can be annoying when people do this, but I can't help myself lol. I wonder if you could operate in a different modality and find discontinuities in material properties rather than use it as a classifier. For some reason skin cancer detection popped into my head, but general purpose inspection/detection cases for any discontinuities might be pretty helpful. Depending on the resolution/size of the field it's inspecting a realtime camera overlay might be interesting for correlation sake.
the FMCW tech makes it impossible to have a resolution inferior to 2.5 cm, (so if two layers are appart, you can't physically tell them appart using physical classical modeling techniques with DSP). However, you can use AI to enhance the performance of the system, and make what you are saying possible. The downside of AI is that you need tons of data, which is expensive to get.