I thought about it more, my biggest problem with PCB is there is only one game in there, usually.
A single arcade machine, when in an actual arcade, is not especially big - so sure each cabinet can have one game in it.
But at home a single arcade machine is relatively huge - and for the amount of space it takes up it must be able to compete with the little Nintendo or PlayStation console under the TV.
Otherwise that giant machine could eventually become a point of wife-contempt "I keep tripping over that damn Defender" and it can eventually become boring because it's only got one game.
But with a MAME machine there are so many games on it there must be a handful that each person enjoys, in fact there are so many that you can (practically) never really try them all. It's an entire arcade in one machine

It's play value justifies the amount of space it takes up in a home.
Emulation always equals more - even Defender's actual control panel, with it's crazy 2-way vertical stick and seven buttons, can still play about 10 games. (I have built one)
Gauntlet's rather limited control panel, with an 8-way stick and two buttons per player can still play about 60 "
4 player simultaneous" games and about 1000 other games.
An arcade machine is about the same size as a refrigerator - but would you keep a refrigerator in your home that only had one type of food in it?
I can understand and appreciate restoring a classic cabinet to it's original state - but I don't think it's practical or versatile enough to guarantee it's own survival.
Well that's my conclusion about PCB, but I am certifiably goofy so it doesn't really matter

I vote to have a Neo Geo control panel on the OP's Defender


I also vote to have a Neo Geo layout and a trackball added to my Gauntlet

I'm going to build a new control panel!

Long live Neo Geo!
OK that's just my 2 cents, worth only 1 cent after tax

Cheers,
Craig
Edit : OK here is what a Neo Geo / Gauntlet CPO looks like :
