I would, but at least one other wildcatter thought of it way before me.
An old shooting friend passed away a few years ago and when his widow was cleaning out his shop she found several boxes of NPE rimfire brass and several different cartridges made from same. I have a couple of them in my collection.
We never could figure out where he got the brass but there were also a lot of other NPE that we wondered about even more, so he must have had an "in" with one of the big-kid manufacturers.
This was years before the recent rash of rimfire factory cartridges.
Small caliber wildcats have a big following of crazy wildcatters. I spent one afternoon with one of them in his shop near Reno and he showed me how to make 10 and 12 caliber jacketed bullets. Much of his work was done with a magnifying glass and if you dropped a 10 caliber lead core onto the floor you just forgot about it.
There's an entire website devoted to tiny cartridges. I can give you a link if you're interested.