Sure, it's easy…just use a downward expander instead of the compressor. In fact, a good way to implement it would be to have the ratio knob allow you to select expansion ratios (i.e. ratios below 1:1). The only difference is that the expansion would have to work below the threshold, whereas compression would be above it.
Cheers
Kris
PS: This capability was available on the TC2290
