Figured out the electrical issue (I am pretty sure, anyway).
One of the extended O2 harnesses was laying against the driver's side header in two places. Not sure how it came loose from the tie down, but it had melted through the insulation (electrical insulation via heat shrink) just enough to fuse the heater wire to the ground (common) wire just enough to create a soft short that would eventually pop the fuse.
The only reason this wire had not become carbon and blown away was because the headers are wrapped. The fact that it was still intact at all is a testament to the quality of the wrap that I used.
I replaced the wiring with a longer extension that could be routed well away from the header and secured it up and out of the way.
Cleared the codes and restarted the engine, seemed to idle somewhat normally (for being cold) and I was able to confirm the O2 voltages were cycling normally as expected.
That said, they seemed a little out of whack and I am concerned that I may have made the driver's side wire too long (I had to tie back a good bit of slack) and am causing an imbalance or something between the two banks.
I need to take her out for a spin this weekend and put a few miles/heat onto the system and see if it is actually acting funky or if it's all in my head, since I've never actually data-logged the car just idling on a cold start...
Also didn't have any proper heat shielding for the wires, so I wrapped in aluminum tape for some radiant protection and have it secured fast against the tranny tunnel and firewall so there's a good 4-6 inches of air between the headers/transmission/engine. (And yes, I left slack at both ends for engine mount movement.)