Instead of running just mame <romname>, you could write a mamewrapper.bat (or other named batch file) that would first apply the appropriate map file and then run the rom as specified on the command line. So, the command line would be:
mamewrapper pacman
The wrapper would apply the map you want for pacman (a 4-way map, I would presume) and then run mame pacman.
Now it is no longer such a manual process.