Too "trick" to be reliable. I looked into this myself when I had (note the past tense) a mini. Was a nice one, too, Douglas barrel, glass bedding, laminate stock. But, the mags would just have been too fussy to be easy to put in. The real problem is the hole system of locking in the front of the magazine. The purpose of the magazine is a quick reload, not fumbling to get it to seat properly. I'd say do it if you really want to be a hobby-machinist. Otherwise, sell the mini and get a decent AR. BTW, the other weak point in a mini is the receiver itself. IT will stretch over time, and could be a problem in as little as 20,000 rounds, give or take. Even if you don't shoot that much (think hom many you would need if you want to be proficient, not just a plinker), it says something. SOmeone once commented to me that "Bill Ruger was a machinist, not a gunsmith." Dunno.
And, if someone is under the PRKaliban, maybe one of those FAB (make/model ?) lowers which supposedly are legal there would allow you to shoot a decent AR top, while the good lower is in hiding for when needed (of course, I mean in a locker in NV).