I took the impatient route and got a new 4 player door, and put in four Canadian quarter mechs.
One thing I learned doing this, is that the mechs are easy to swap in and out. And the switch that fires when a coin is accepted is independent of the mechs (it comes as part of the door itself). It's much like the switches in most buttons, and under most joysticks, in that it has a common, NO, and NC. This makes it really easy to wire these to your keyboard encoder and trigger Mame.
If I had to do it all over again, I'd consider token mechs. While I do have a bucket of quarters ready to be used, I can imagine a day when a group of younger ones want to play, and decide that the quarters have more appeal than the games. Tokens would be far less likely to walk away en masse - I'm guessing. And those BYOAC tokens look cool - if you can get them.