Mako, I have read some of your other post and have become a big fan of your work. You are very talented. Thought I might have an idea to toss out for you. I do not know if it will help or not. Years ago me and my friends use to play on different board types and I was anal about my bases matching the boards that we were playing on. So I ended up making a lot of bases for the different types of boards. Then I was making them interchangeable. I tried magnets at first and worked some what well. What I found to work the best for me was notching the bottom of the slot on the slota base. Basically I would put a T type pin in the mini. Then on all the bases I would have enough space the the T part of the pin could slide through. Then on the bottom of the base I would notch it so the pi would clear and had a slight ramp up to the center of the slot from the opposite directions. The top of the T would only go down about half to 3/4 of the depth of the slot. This way the base was not sitting on the wire.
This way when i wanted to play on the board I would just grab what bases I wanted. Insert my minis into the base and do a 1/4 turn and they were locked into the base. It is just and idea and hopefully it might help with some ideas. If you want more information on how I did the bases just let me know. Have a great day and keep up the awsome work .