freeloader is that GC mod, right? with the 2 switches? thats pretty nice... I was shocked that they got to modding them that easily.
I doubt its really that technical to do it... but get someone that knows how to sauter
PS1 needs one of those codebreakers or back panel modchips to run imported ps1 games. But those are only for the older ps1 models that have the port in the back.
Ps2 however needs either a mod or a fliptop. Flitop is just a bootable cd, and a covverfor your ps2, so you just open up the top... I believe it doesnt play ps1 backup games however, so modding would probably be your best bet... which requires some major sautering. And that still wont help with some anti-mod ps1 games. (an import of Ore no Ryouri will not run on a modded ps2... *sniff* *sniff*, but will run on a codebreaker'ed (or whatever'ed) ps1.
GBA... hell, just get a flash cart. Itll play anything... I dont think its region encoded, either...