I could see that for some people. Comes down to price as it always does.
How about this. My bet is folks buying your cabs are doing so to rebuild a game they have, probably complete or close to it, in a junk cab. I would think you may move some cabs assembled and painted minus all the hard parts. That would keep you out of the control panel, hardware, and bracket repro game. Perhaps an upgrade with side art. If you can work with an art supplier you could step up and offer a complete art package.
I will use myself as an example. I have a complete Qbert. Working board and all. The cab is absolute trash. I have looked at your cabs but just can not get excited about doing the paint work. If you offerd one ready to go, again perhaps with a one stop shop art pack, I can see being more excited about a purchase.