Having the option to use Vigor in some spells

While all special moves in vanilla ignore back row, some vanilla special moves (for example, Dispatch) do indeed use vigour in their calculations, and that can be modified in FF3usME already fairly easily. Go to the spell editor and under "Special 1" you'll see a box for "Physical Damage".

I'm pretty sure Nattak got the code for allowing special attacks to respect row from Synchysi. You'll have to ask one of them about that.