Also maybe I'm thinking about this wrong, but if you mirrored the screen wouldn't it make the spinners seem like they are working backwards? Just do what romshark said.
Mame has option for reversing direction. That was not an issue
If mirroring just screen 2 did still actually happen (maybe to help follow the ball from one screen to the other. I don't have that setup so I'm not sure how it plays), it should be an easy fix. Just [TAB], Analog Control, and reverse paddle for 3 and 4.
At least, I think that would fix it. I don't have paddles or spinners myself to try this with.
If Joysticks are being used instead, just reverse the left and controls for the player.
From this quote I gather that you haven't play this game in arcades. It's a single screen 4 player game (I haven't even seen original 4 player arcade cabinet, only 2). Nothing travels between the screens. Imagine 4 player breakout.
I have the game cloned on 2 monitors. It could be played where 2 bottom positions are played by 2 players on one monitor and 2 other top positions, played on 2nd monitor. Then there is no issue. But I rotated the screen (playfield) so all players can be on the bottom so position [3] [4] on top rotated 180 is now [4] [3], but the control panel obviously is not.
Simple mirroring option in MAME video options would solve it. And it wouldn't affect anything because the text is displayed upside down as well.
Another game where screen mirroring would be great would Hot Shot. Me and my buddy both came to conclusion we prefer to be on the left side (although text would get screwed up, but that's non issue for us)
Maybe it'd be simpler to swap the controls. Just change the p3 controls to p4, and p4 controls to the old p3.
I have to think about this one. I'm not even sure if my wiring would allow me for easy swapping positions. It would be much easier in software.