The benefit of pointing to an existing script is that ypu don't risk forgetting something, changes to how a move ends will be more consistent, and you save space by not recompiling the same code multiple times when you can simply reuse it. In terms of function, though, no, there's no real difference.
Yeah, Gaia can be used as a ROM base provided you credit whoever I have and the other clause is I'm too lazy to share relevant. ini files haha
But yeah, go ahead. fwiw a lot of those items' effects are documented here on PC.