I think lets step it up a notch if possible and have acrylic, steel, alu plates along with PCB only, as these are important factors as well.
Although I like that idea, all that would increase the cost of manufacturing and maybe also shipping the tester since it will need to get bigger. I would do just an alu or steel plate since now most boards come with one (is there a popular board without a successor yet that is not plate mounted? I know there's the KBT Race, but afaik it's out of production). This thing might get lost during shipping so I would like to keep the costs low.
Multiple switches with various springs swapped. Costar stabs, Cherry plate and PCB mounted stabs with modified cherry stabs as well.
What about: Red, black, vintage black, brown, clear, ergo clear (65g and black spring maybe?), blue, green, white, Matias Quiet, Matias Clicky. That could be a neat 3x4 array. Did I miss something major?
Different Stabs would be nice, but because of the reasons above maybe just Costar and Cherry plate mounted.
Keycaps separate, so they can switches around or feel on different types of switches.
I would include a little keycap puller then. If you don't have one spare, just a DIY one should do the job.
I think we should have 3 parallel tours, US+Canada/Europe/ROW
I would like that as well.