Considering the amount of modification that would be needed to effectively incorporate an existing woodstove into an RMH vs. the effort of building the RMH from scratch, I don't think it would be worthwhile in most circumstances. Generally you will be able to get the exact layout/configuration you need better if you don't have old sheetmetal to work around.
Wiring in walls should not be an issue, as the walls themselves need to be protected from heat as much as the wires do. Outlets are another matter, and you may need to either relocate the outlets higher in the wall if practical, or make a "pocket" in the back of the mass bench that lets you access the outlet. Even if you eliminate an outlet, you need an accessible junction box where the wires meet.
Thank You everyone! Hopefully I'll get better at searching through the site.
I only glanced over the material in the links, but I'm pretty sure after looking at them that I'll look at the stoves
As things I can cut up for parts to "accessorize" my build (whenever I can manage it).
Any extra issues if you run the bench under windows?
Also was thinking of running some kind of tubing through the bench to recirculate water for cooling in summer and maybe additional heating when it's cold.
A) Good notion?
B) Don't even think about it, it won't end well notion ?
C) (Said in Frasier voice) MY GOD WOMAN! STEP AWAY FROM THE TOOLS BEFORE YOU
POKE A HOLE IN THE SPACE/TIME CONTINUUM!" notion?
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''