What LR3 components would you machine if you had no restrictions?

[azab2c]

Lots of considerations for a removable core, sounds tricky.

LowRider v3 CNC - Tool-less KINEMATIC Accessory Holder for LowRider 3 CNC 4.0

You want the router as close to the Z as possible. Any distance away and the force on the gantry will be twisting, to the side, and not pushing up. So that’s the first reason not to have a quick change mount for a router. The second is that you want this mount to be as rigid as possible. If you really want a square setup, you probably also need to have some shims to adjust the final alignment, and that has to be rigidly mounted. Any flex or slop in the mount will be bad for accuracy. That said…