I tried...
Problem is, when I apply the stencil to the lower, then laser it, there's an invisible layer of adhesive that isn't burned off and you won't know until you apply current. By then it's too late. With really small details (which is really apparent on Chinese characters) you can try to transfer the vinyl and only parts of it will transfer. So after several tries, and sanding it off when it just would not cut it, I give up... I can only do this so many times before the lower looks like it's got its serial number wiped off... and that's bad because anyone in Law Enforcement sees that is going to confiscate it and send it to a lab to determine that, while I sit in jail trying to prove my innocence (while they figure out what other obscure laws they can charge me with).
This guy sells a lower that's been engraved with a fiber laser...
https://www.atomicengraving.com/product/ar15-80-forged-lower-clone-republic-china-taiwan-t91-replica/
At 99 dollars it's a little steep considering I got a bunch of Tactical Machining ones I got that costs way less...