Swinksy, I always thought the easiest way to do a custom pinball, is to find a basic machine like a 1978 phoenix, or a similar designed machine that has 2 x different audio styles to chose from (ding dong chimes or space invader style noises) and just do a custom job on the cabinet and decals, and just completely sand back the playfield and re-do yor own artwork,whilst keeping all the exsisting hardware, which would work perfectly.
Doing anything on a DMD wont really work cause the audio is specific for that title etc. Have u thought of grabbing a late 70's machine and doing a custom pinny that way ?