How bad could it be? It's reversible, right? Just install after-market legs and side rails if you need to go back for resale later? You could even keep the originals and have after-market ones coated.

Given what a good-condition TZ costs, a few hundred dollars for the parts and coating so you can enjoy the game more while you have it seems like small potatoes. I wouldn't personally do it, but if it's what you like, why not?

As you can see from the description, since you don't have the 3rd magnet installed (with the opto), it doesn't matter what you set it to. The game will act as if you have set it to "NO". You can set it to whatever you like.

You could just buy new ones: https://www.ministryofpinball.com/en/twilight%20zone%20plastics%20set.html

The shop is in the Netherlands, but I'm pretty sure they ship to the US.

Actually, it's a flush trim router bit. But yes, I can see how that would work well. Those are very handy for trimming one material laid on top of another that already has the desired profile.