UPDATE- 5/16 @ 3:05 PM: The peg and baseplate ended up being a bit loose, so I've replaced all the files, and now it's working like a dream-

Hey, folks. Before we head into the weekend, here's a (very) experimental spiral staircase prototype. All of the parts print support free via FDM. When assembling, choose the step peg for the height you want (50mm, 75mm, or 100mm) and drop it into the baseplate. Then, alternate steps A and B so they overlap a bit as shown in the image by sliding them onto the octagonal peg. The number of steps you'll need (in addition to the base plate) depends on the peg you use. (9 steps for 50mm, 14 for 75mm, or 19 steps for 100mm.) Each step should support a miniature with a 3mm tall base (the standard, especially for laser-cut bases). We'll be testing this one out this weekend, but it should be good to go. We'll update with a new prototype if we make any alterations.
Have a great weekend!
- Dutchmogul