Hi Brett,
Regarding the vinyl film from usa (which appears to be nothing more than signwriters vinyl here in oz for $15 a roll).
I'm concerned that being so thin it will contour to all the imperfections of the cabinet side, thus creating a not-so-flat mirror effect, but rather a shimmery/distorted effect, which may or may not be ideal and will differ between users preferences.
While acrylic mirror (perspex) is thick at 3-6mm, there's nothing to stop us from routing the inside of the cabinet wall out, to house the persex, which is about $5 per blade ;-)
A channel could be routed in such a way that the perspex simply drops into a slot, and easily replaced if damaged, in case the ball has access to hit it...
In fact you wouldn't need to lift the playfield, juts slip the top-glass off and drop in 2 new blades and you're done...
just my thoughts, in case it inspires anyone ;-)
MM.