That's awesome!
I don't suppose... could it be modified to use the spell power of the spell? 5 * SP? So like, if the spell power was 5 it would heal 25 HP, or if the spell power was 20 it would heal 100 HP or whatever.
I figured it out! I was looking through the Tower of Bab-il Docs and saw this...
"At the time this subroutine is called, the target's data has been copied to
2700-277F in RAM. The caster's data has been copied to 2680-26FF. The
subroutines modify this data. The relevant spell/item table entry has been
copied to 289C-28A1. 28A2-28A4 "
That tells me exactly where the spell data is in RAM at the exact time I need it. 289C was what you were looking for. For just a Brief second the game puts the spell's power and accuracy into 289D, but that brief second is all the time the Life formula needs to grab its spell power and revive an ally using its spell power as a base.
You would change this...
$03/D6D9 AD 16 27 LDA $2716 [$7E:2716] A:001D X:0002 Y:0005 P:envMxdizc - Looks at 7E2716 which is a copy of the fallen character's stats. This is the fallen character's Modified Vitality
To this...
$03/D6D9 AD 9D 28 LDA $289D [$7E:289D] A:001D X:0002 Y:0005 P:envMxdizc - Looks at 7E289D's value which is the where the power of Life and Phoenix Down will be stored. Then this becomes the fallen character's HP * 5. This also effects anything else that may bring a fallen one back to life (ironically though this should fix the enemy vitality = 0 glitch from the original game.
This change also appears to have the strange effect of taking hit percentage into account, since it uses Spell Power as its base.
And with this you can make Phoenix Downs and Life Spells heal different amounts.
In ROM just change...
0x01D8D9 - AD 16 27
To....
0x01D8D9 - AD 9D 28