If anyone wants to know how to build one on their own pm me
You, sir, are a goddamn hero. I cannot believe how cool this mod is!
If I may make a couple suggestions, as a Vectrex fan, I would add a second analog joystick and 4 buttons on the control panel, there are some games (like Space Wars and Rip-Off) that allow for 2-player simultaneous play. As someone else has suggested, I would disconnect the Vectrex's monitor while it's in the cabinet, no need to add wear to it. I don't know if you can come across a broken/unsalvageable Vectrex but, if you do, I'd cannibalize the cart slot and wire it into the control panel so that you don't have to keep bending down and accessing the Vectrex through the coin slot door. Or maybe there's some other way to allow for a slot of some kind so that you can plug in carts.
Of course, the ultimate set-up would include making full-size overlays for the various games, haahaaha. That would be a tedious hell swapping them, I know. I wonder, is there a type of LCD display that is see-thru when it's off but can display images that are basically transparent, sort of a digital overlay screen on top of the CRT? That would solve all the overlay problems. They're not necessary but they do add to the experience.
I would also suggest a custom cabinet that looks kind of like a giant Vectrex. Meaning it's mostly black and is sloping back slightly like the way Tempest is shaped (though with less back slope). Actually, looking at it, it has a sort of Cinematronics Space Wars shape to it, too.
Again, this is incredibly cool, glad you shared it.