ok so what we can do is attempt to piece something together
i found a nice breakpoint at 3F04E (specifically, 3F05C). what the function does is check for hustle and then apply hustle's boost. what we can do is branch it off, and then apply hustle's boost in our own little thing, which should be simple enough. (i already have hustle's boost tracked down in an asm snippet, so no worries)
it was also used by mrdollsteak to implement sniper, technician, defeatist, and slow start, and is located in the middle of the move_damage_calc function. i can not find the references to overgrow/blaze/torrent within the battle scripts, which kinda sucks ahaha...
btw do you know if we can use something like battle script pro to code the abilities? that would make like everything 999999999x easier. i'm assuming we can't because no one has, but yeah...
i understand that some abilities would be handled by certain moves, but not this type, ahaha...
if we wanted to do this in the worst way possible, we could just go to every move effect and add in a check for if hp is below 33%, and then branch off to a routine which checked for ability and then checked type and FINALLY modified the desired output by using tlachti's damage modifiers or something
this would work but would be um not as nice as, say, being able to do this asm