Yeah, I would love a keyboard like this except that I've now moved entirely to corne-ish zen. I wish I could have a corne-ish zen with a trackpoint, but I expect the people who would like that must be a tiny niche-within-a-niche.
you could technically slam a trackball onto an ergo split keyboard. wouldn't recommend it but you could. people tend to put one between their keyboards so why not just build it into the right one?