I bought all the GBA FF games off eBay and only received counterfeit ones :-/ At least the ones I got don’t have batteries in them. Saving makes the games freeze for a small time but other than that they are working.
Completed the FF V GBA counterfeit on a DS lite. Ended up playing through the DS versions of III and IV, also off eBay, which do not seem to be fakes fortunately.
No matter which model you get, do replace the internal hard drive with a SATA SSD. Virtually any SSD will do since the bus speed is the limiting factor on PS3
Later revisions of fat models dropped PS2 hardware components and should be cheaper to obtain. Depending on which PS2 games you want to run in addition to PS3, the built-in PS2 emulator can still be good enough on these. There is a game compatibility list somewhere for PS2 emulation on CFW.