Not really a good idea. Just get the cheap k40 and work your way around the issues.
It’s all about the tolerances. Just not going to get it on the MPCNC.
I have had a bunch of k40 lasers go thru the shop the last few months. Wonderful machines once you grok the operation of them, no need to butcher it and use it for parts. The bigger ones are relatively cheap too.
MPCNC is not really a machine I would count on to get 10 micron tolerances without maybe using some good quality chromed hydraulic shafting.
Rather it is a lower cost machine, suitable for wood working, aluminum machining where tolerances are not super critical, signage, and the like. Even CNC plasma looks like a suitable use as plasma seldom gives me sub half mm tolerances even on expensive pro machines I have used.
It possible to get one of these really dialed in, but it’s going to take a fair amount of effort, and a good dial gauge and you will need to be doing some re-adjustment quite often.