So, you want to make two separate units?

That's the only practical solution I can think of.
As for plugging the PSX into the DVD player and use its screen when your friend isn't watching DVDs, as long as the DVD player has video
inputs you just have to leave the AV Out jack on the Playstation.
Cpt K1ll3r wrote:Do you think I could combine a bulky, broken portable DVD player with a PlayStation One to create one machine which does both?
Sony already made a Playstation / DVD player combo unit. They called it the Playstation 2.
The original Playstation (PSone included)
cannot play DVDs. The Playstation and DVD disc drives are
not interchangeable. The only way you're going to make a Playstation/DVD player combo portable with one disc drive is to make a portable
PS2.
Also, there's no reason a portable PSX or PS2 should be the size of a briefcase, as your mockup suggests.