If you think copper bands touching with a magnetic mount to hold it in place is going to work reliably, good luck with that.
I’ve seen some Tetris-y blocks that did a simple 2 wire connection (power only) via touching pads…
And you’ll see how fussy that is. Now try adding a data line, which BTW, you can’t fork with normal WS2812s, without losing individual addressablilty. (Yes, you can use the mystery LEDs which will handle this, see my post re that).
Good luck with it. It’s not going to be easy to make it so good that it’s not frustrating and perhaps even a danger as above.
Keep in mind that NanoLeaf etc all use tabs not merely magnetics so they depending on friction fits, and they don’t design them to be moved around a lot.