... and run some experiments. Stay tuned
I'm following this thread closely. I've been thinking about a specific build for some time now, it involves an HHKB and some mx keycaps (nothing special). Novatouch sliders would bring the price too high that's discouraging for me to purse the project.
I also read a blogpost (I'm new, I don't know if I'm allowed to link it here) about 2019 niz switches (old ones seem to have a bigger stem, some users reported them damaging the keycaps) which, apparently, could be a good-enough fit yet not a perfect one.
Finally, as you said in another post, stabs may be the biggest limit.
Anyway, thank you for experimenting and I really hope to hear some feedback!