The non-magnet version is essentially the same as the LiPo right? I wonder if your option 2 is closer to the truth!
Not really - the frame is smaller in the 18650s than the LiPo - so it's not an interchangeable switch, you still have to have the battery tray, it's shallower, etc. And the main body has to have wings enough to hold that sled and slide on from the bottom.
I mean this is all 3D printing on-demand I guess so maybe it doesn't matter at all - overthinking is still where I'm at but I find it curious in any case. -Mags