I agree that pre-made metal panels would be pretty neat, I was even considering it for my own cabinet. However, in order to make them affordable they would need to be fabricated in volume. I would imagine a typical 2 Player, 6 (or 7) button layout with a 3" trackball between the players would be about the most universal layout that you could come up with that would suit most builders. I think a bigger concern would be the overall panel dimensions. So many people have different sized cabinets, either scratch-built or converted, that I wouldn't be sure how to size it so it would fit most people's requirements. Any other characteristics such as bends or lips in the panel would just increase the cost and be more of a hinderance than an advantage to a lot of people, too. I think quite a bit of research would be required before I seriously look at this one.
If I were to go ahead with the joystick mounting plate I would be sure to include mounting holes for all of Ultimarc's sticks, that would be a given. I'll have to think about this one some more, but I believe that there may be some potential here. I'm in the process of developing a couple more products right now, so these plates would come after those if I decide to do them.