[dcb]

Emission testing weirdness aside...

Leaving the heat in the cat sounds like an interesting solution, i.e. wrap and not dfco (forcing "cooling" air through the converter).

Main thing is not running it so hot that you destroy the substrate, i.e. extended cruise. If you want to get fancy add liquid cooling to the TWC (that could get dangerous with 1000+ degree coolant) and manage the TWC heat better that way.

i.e.
you are driving, too much heat building up in converter, move some heat to a small radiator.

Engine shuts off, leave hot liquid mass around the converter and inlet, put some liquid in a thermos for restart.

Figure out a way to let it heat up "dry" when cold, coolant added to thermal mass as TWC efficiency allows.

Chemical bootstrap or no, the bottom line is getting back up to temp quickly.