Thanks floraluk! This is timely in a strange way. [FWIW, I was thinking the BBC article referred to Sequoia, not Sequoiadendron; I'd forgotten the convention that giant + redwood refers to the inland Seirra Nevada species. It would be simpler if people just called interior one the Sequoia, and the coastal one the Redwood, which I believe is the more common parlance within California - General Sherman is within 'Sequoia National Park' after all, while 'Redwood National Park' is the coastal one!]

Someone just emailed me last night about a nursery in the southeastern US (not Camellia Forest, so don't bother them, although they would be a likely suspect) that has just successfully grafted a batch of Sequoia sempervirens onto Metasequoia glyptostroboides! Although California Redwood is already surprisingly adoptable to the SE US, grafting onto Metasequoia would at least reduce the requirement for well draining soil.

I had no idea if or when they will be for retail sale. It's possible this company will wait until they are relatively large specimens that can be sold B&B to upscale clients. I will provide more details as I get them.

Also, yes, I do have the cognitive abilities to recogize at least one potential 'elephant in the room' type problem about this - MS/DR clearly goes fully dormant in winter, S.s./CR less so. So will these trees survive long term? Also something they will have to figure out.