Hello Romhacking community!
As an introduction, I have no experience with any romhacking, so please correct any wrong assumptions I make.
How viable is it to replace the FFIX PSX FMVs with the Steam FMVs? From initial research the PSX FMVs are in a SRT format, containing an avi files.
However, I don't know if it's possible to import new and bigger SRT files into the rom. Given their higher quality they will be bigger files, and I don't know if roms will allow that, as I've only seen other FMV hacks have a 1:1 substitute.