I use original cabinets all the time, but I only use the RIGHT cabinets.
First off, if it is working, then forget it. (Unless it is a fairly trashed mis-matched conversion, like a black painted pac-cabinet with Contra marquee running a Gals Panic board).
Dead conversion titles are generally open season, although I DO try to keep the original conversion artwork if possible.
Dedicated games are more complicated.
Dedicated working, forget it, keep it as is.
Dedicated dead (but complete), MAYBE usable for Mame. Basically you need to take a reality check on what the game is. What the game is worth. How much money it would take you to repair the game, and if you would want the game once fixed. I do often support simply replacing a dead PCB with the computer in these instances. Fact is that a Pac, Galaga, or Williams PCB is REALLY expensive, and the computer can play the same game for cheaper.
Dedicated incomplete. Same questions as dedicated, dead.
Dedicated stripped. Usually open season for Mame here. There are VERY FEW games that it makes financial sense to build from the ground up when all you have is a piece of wood.
In all cases of dedicated games, One major rule applies
#1. Do not paint over the sideart, enlarge the control panel, or otherwise modify the cabinet. If you are not happy with the original control panel, then simply remove it and make a new one to replace it. Do your absolute best to make sure your results look like the original game.
A few examples from my own LONG maming history.
Galaxian/Pac cabinet. Was Clutch Hitter (painted brown) when I got it. Eventually got a Pac-Man marquee, bezel, and control panel, and ran only 4-way games.
Amazing Maze - Was complete and dedicated, but dead when I got it. Boardset repairs would have run me $150. There is ZERO demand for this game. The repaired game would not have been worth the $150. I sold the monitor and boardset for far more than the working game would have been worth. I removed the original panel and set it aside (still have it too), and made a new panel with the standard SF II layout. I used it for a LONG time this way. It was recently de-mamed though. I plan on putting the original panel back on, and redoing it to only have games that can play with the controls it has on the original panel.
Battlezone. I was doing this to look all original outside, but be all computer and VGA inside. Cabinet came to me complete minus PCB, minus monitor. A quick ebay check tells me that the monitor and PCB are worth more than the complete working game. So I went the mame route. I never quite finished the project though. I got the monitor installed, and lost interest. I listed the incomplete project on ebay, and the buyer ONLY wanted the panel and periscope plastics, so now I STILL have the cabinet, only far less complete than before.
Defender - Was empty cabinet with sideart. I got a repro marquee, an NOS Willis Defender overlay, and made it into a Mame powered Defender. It ONLY runs Defender right now, and I never actually got around to giving it a dedicated computer, so it is still in project mode.
Space Firebird - Was mini. Was complete, and worked, except for one problem, missing shot animations. It is a common problem, and no one know how to fix it. I sold the insides, sold the cabinet to someone else to Mame, and then was given the cabinet back six months later. I changed only the joystick externally (switched 2 way for 8-way), and eventually sold this game complete at the St. Louis auction.
I have more examples, but I think you guys get the picture.
For those of you that DON'T want to build your own, but don't want to "tear up" an original either, then there is still one big option.
Non-collectable machines.
Trivia machines.
Gambling machines
Tournament Solitaire (ONE OF THE BEST cabinets for Mame, has serial trackball already, has VGA monitor already, has room for two joysticks and buttons).
other commericial units that resemble arcade games, but are not.
This gambling and trivia stuff has no real collectors value. It isn't like Pac-Man, where the new stuff will NEVER replace the old stuff. With gambling and trivia, the new stuff is ALWAYS better than the old stuff.