I don't really follow the modelling scene much, so I'm not sure what you'd specifically have to do, but the impression I get is that you would have to radically alter the executable to get these models working. That's a mammoth task, especially for someone who - no offense - has only ever put little-endian integers into a cheat engine and hopes he'll find them in RAM. Assembler is not simple, or easy to pick up. FF7's AI code is a sort of simplified assembler, so practicing that with a bit of, say, C might offer you the first steps you need to take.
But even then, it would be a tremendous task to alter the engine to accept even marginally different sorts of models. Frankly, I wouldn't bother.