>>19614752Let's do some comparison shall we?
Kyogre can use Water Spout, an 150 bp move at full health (or Hydro Pump, a 110 bp move) and receive STAB and rain boost in one turn, a special move off 150 Special Attack, hitting Groudon for two times the damage on his 90 Special Defense.
Now, let's use your idea. Groudon can use Solar Beam, a 120 bp move, that doesn't receive STAB or a weather boost except that it can be used in one turn IF the sun is out, a special move off of 100 special attack for two times the damage on Kyogre's 140 Special Defense.
You don't see any imbalance here?
Unless Groudon is spec'd for Special Attacks specifically to fight Kyogre, it fucking dies.