Here is my Team:
Mewtwo LV100
Psychic
Shadowball
Fireblast
Solar beam
Mewtwo's moveset is reasonable, but I would recommend changing Solar beam to a Fighting move to get rid of those nasty Dark Types. Although it would have been better to get Flamethrower instead of Fireblast, it is useful to get rid of Bugs, so I'm not complaining.
Rayquaza LV100
Outrage
Surf
Fly
Hyper beam
Rayquaza has a tterrible weakness to ice types, so another Flamethrower, or some electric move would be better than Surf. Even Hyper beam could be changed with Extremespeed, because it always attacks first, and doesn't miss a turn.
Charizard LV100
Flamethrower
Fireblast
Blastburn
Slash
This looks like the Charizard that I had ages ago. Let's go through this. Charizard is terribly weak to Rock and Electric Types, so I would remove Fireblast and replace with with Earthquake/ Flamethrower is good enough. Remove Blastburn and replace with a Flying attack fro STAB
Raichu LV100
Thunderbolt
Thunder
Shockwave
Bodyslam
Remove Thunder. 'Nuff said. Replace it with Brick Break, or Focuss Punch to knock out those Rock/Ground combos like Onix. You don't need Shockwave, because you already have Thunderbolt. Change Shockwave with something like Flash, to lower the accuracy of those Ground Types.
Ditto LV90
transform
I can't change this one, can I?
Ho-oh LV70
Sacred Ash
Fireblast
Fly
Safeguard