I've always wondered if NEC officially did this (make a arcade version of the console) in Japan. I've seen a few listed on YAJ but they always seem homemade or prototype looking.
From what I can tell, the Irem M72 board had a lot of ports to obey...it's kinda like the ST-V and Saturn (or Namco System 11 and PS1). Having the Irem hardware already out there, might have made making a PCE arcade board kinda silly. Of course we have that Bloody Wolf one off board from Data East that (I'm told) is a beefed up PCE.