Tim for reasons we can only guess and Cotic probably won’t disclose, it seems they don’t want to make what you want. Perhaps they feel their time and energy is more usefully invested elsewhere, but that’s just conjecture. Right or wrong, that’s their privilege.
Also, speaking as a lower-medium height person, who’s too small to make the best of a 29er IMO, I think Kelvin’s point is valid. If a 26er fits me nice, surely someone your height would be better on a 29er.
But if you know what you want, go get a frame builder to make it for you. In essence, it’s a bunch of metal tubes welded together, it’s not magic. You can do what you want really, (other then use someone else’s trademarks, so you can’t call it a Cotic).