For moves like Blast Burn, Hydro Cannon, Psycho Boost etc. I know some pokemon might not have a strong move because some are legendary moves but when your like lvl 100, you can learn a legend move, for example: If I got Gallade to 100, i can learn Psycho Boost. if there are no legend moves for other types of pokemon for example: Ground. They can learn Giga Impact or Hyper Beam.
It might not be a good thing but im just suggesting it.
Technically not possible (other than Devs+ teaching them selves it) as all Pokemon are linked to the BW1 Pokedex move-sets. Besides a lot of legendary moves are overpowered.
The elemental Hyper Beams are actually only mildly more damaging in Mystery Dungeon then Hydro Pump/Solar Beam/Fire Blast/Stone Edge/Ect. or whichever move you decide on forgoing for the full-powered equivalent.
This is due to the fact that Mystery Dungeon’s star system calculates attacks in a radically different way then that in the main games.
An attack’s actual power rating holds little water when compared to a Pokemon’s actual attacking stats and the defender’s defenses, which explains why Bullet Seed is so lethal in PMD and why Hyper Beam is underwhelming even on Adaptability Porygon-Z.
So in conclusion, the Elemental Hyper Beams aren’t anything special at all, and they should be included if only to have so fool take them up in order to gain a marginally more powerful yet impractically crippling move to show off how devoted they are to the game. And for bragging rights.