Thank you,

The arc fault stipulation could be the monkey wrench that pops my conservative bubble. My electrician friend mentioned that I will need arc fault breakers...

But... the one 14-3 is long enough that I could just use it to power my newly installed radon fan and call it a win. The other 14-3 would be hard to salvage since it's broken up to power existing lights anyway. I can easily rewire it the way I want to and just abandon the circuit when I'm done.

good luck- jim