Mac, yeah, uprights are easy, and Midway cocktails are easy, school desk cocktails are TOUGH. Some of them even have curved pieces of wood on them.
But, you can bring even the cruddiest one back from the dead fairly simple. My Time Pilot looked like updog when I got it. (I actually bought the monitor from the guy and he threw in the cocktail for free because he didn't think it was salvagable).
First off, pull off ALL the black metal and strip it using a wire wheel drill attachment, then repaint gloss black.
Scrape all the paint off the underside of the glass with the exception of about a half inch around the monitor cutout (that seldom flakes, and you are never gonna mask those curves correctly anyway), mask off the middle, and repaint with flat black.
Cut off those rusted, nasty, likely half missing leg levelers, and go to the hardware store and get some new furniture ones (the ones with the felt bottoms are great for cocktails).
Those few steps alone will make a world of difference. A good overall cleaning and some shiny new joysticks and buttons will do the rest.
If you ARE going to attempt to scratchbuild one, then I suggest first shopping around all the local thrift stores and garage sales and looking for SOMETHING that has suitable legs on it (coffee table, desk, etc), and then kind of winging it from there. An exact copy of one of the original tables would be WAY too hard, but if you can get some decent legs, then you could make something close. I simply cannot stress enough how many parts these things have on them that would require advanced carpentry skills and a metal fabrication shop.
On the other side of the coin, easiest cocktail table to build would probably be the Cinematronics one, it doesn't even need tempered glass (they shipped with silk screened plexi). Look around on arcadeflyers.com for some pictures (kspiff also owns one that used to belong to me).