Welcome aboard!  Unfortunately, I don't recall ever seeing any info. on this particular beast, but Mr. Covell (ccovell) is knowledgeable about a lot of oddball hardware and might be helpful.  It's your equipment so do as you wish, but I vote that you don't modify such a funky piece of hardware (assuming that it's rare and pricey).  Like you stated, PC Engine games are readily available and usually cheap.