When that Kishu gets older, you might try pollinating the flowers with the pollen from one of the other cold-hardy varieties and then try growing the seeds. Kishu produces all zygotic seed so is a good choice for female parent if you're trying to hybridize. You might be able to make your own new cold-hardy citrus variety. Kishu also has the advantage of loose easy to peel skin. Kishu though isn't really a cold hardy variety.

Here's keraji, yuzu, and mandarinquat

Mandarinquat is kind of an interesting one, it's almost as hardy as kumquat. For Indio mandarinquat, one source says it is hardy down to 26 F, although I strongly suspect it could take a bit lower, possibly even into the high teens. There was an old post on The Cloudforest Gardener that said it didn't survive 17 F in the PNW. A less common variety, Nippon mandarinquat may possibly be hardy down to as low as 14 F.

Yuzu has very little problem growing outside unprotected in the PNW, if it's in a sheltered spot.

I was thinking along those lines but I wasn't sure which combos. The kishu bloomed wonderfully in January and did pretty well under the lights, but it was too young and spindly all fruits dropped, its fattened up a bit, starting to bloom now. I was thinking of using the Thomasville if I ever get it to bloom