[Scripting Question] [16.2] Special Moves for Megas

[ArchyTheArc]

So the title might be confusing/why would i need to make this for that.

basically i want specific move(s) to change when a pokemon mega's, E.G. Flamethrower becomes Blue flames when it becomes charizard X (the fire/dragon one) etc.

i've used code for the way the galarian legends change moves based on form, but since that uses the start of battle than mid-battle (moreso for the form change however) i cant seem to make it change.

Spoiler:

MultipleForms.register(:CHARIZARD,{
"getMegaForm"=>proc{|pokemon|
   next 1 if isConst?(pokemon.item,PBItems,:CHARIZARDITEX)
   next 2 if isConst?(pokemon.item,PBItems,:CHARIZARDITEY)
   next
},
"getMegaName"=>proc{|pokemon|
   next _INTL("Mega Charizard X") if pokemon.form==1
   next _INTL("Mega Charizard Y") if pokemon.form==2
   next
},
"getBaseStats"=>proc{|pokemon|
   next [78,130,111,100,130,85] if pokemon.form==1
   next [78,104,78,100,159,115] if pokemon.form==2
   next
},
"type2"=>proc{|pokemon|
   next getID(PBTypes,:DRAGON) if pokemon.form==1
   next getID(PBTypes,:FLYING) if pokemon.form==2
   next
},
"getAbilityList"=>proc{|pokemon|
   next [[getID(PBAbilities,:TOUGHCLAWS),0]] if pokemon.form==1
   next [[getID(PBAbilities,:DROUGHT),0]] if pokemon.form==2
   next
},
"weight"=>proc{|pokemon|
   next 1105 if pokemon.form==1
   next 1005 if pokemon.form==2
   next
},
"onSetForm"=>proc{|pokemon,form|
   moves=[
      :FLAMETHROWER,       
      :BLUEFLAME  
   ]
   hasoldmove=-1
   for i in 0...4
     for j in 0...moves.length
       if isConst?(pokemon.moves[i].id,PBMoves,moves[j])
         hasoldmove=i; break
       end
     end
     break if hasoldmove>=0
   end
   newmove = moves[form]
   if newmove!=nil && hasConst?(PBMoves,newmove)
     if hasoldmove>=0
       oldmovepp=pokemon.moves[hasoldmove].pp
       pokemon.moves[hasoldmove]=PBMove.new(getID(PBMoves,newmove))
       pokemon.moves[hasoldmove].pp=[oldmovepp,pokemon.moves[hasoldmove].totalpp].min
     end
   end
}
})

any help would be nice, i know if you use the basic "onsetform" move function in the default way/rotom like way it comes up with the "____ wants to learn..." etc.

another method could be a way to see like "if charizard holds charizardite X flamethrower becomes blue flame" (since it'll be flamethrower until second turn)