My first OCS A500 from 1987 was permanently stuck in NTSC mode. Then one day in late 1988 or 1989 A500s started quietly shipping with "Fat Agnus" chips. Soon afterwards, the Fat Agnus chips went on sale separately and you could put out your old Crap Agnus and replace it with the new Fat Agnus. Then your Amiga suddenly became able to boot into either PAL or NTSC or even to switch in real time while running.
I used to switch out Agnusi back in the day for lots of friends.
So we just need to switch out the lame OCS Agnus in the Minimig with a shiny new ECS Agnus.
And while you are at it, go ahead and make it a SuperFat Agnus(tm) that can address 8 MB of chipram so the tremendously expensive cost of the minimig might be justified.
Problem solved.