I played Ubers for a little while and there is a problem with this.
Mewtwo's Solar Beam might get some surprise 2HKO's against Groundon, but it's unlikely. PDon which switch out after getting hit by the first, leaving Mewtwo open. Also, if the Pdon just decides to attack then it's probably going to knock out Mewtwo in one attack.
The same goes for Kyorge. Thunder won't beat it in one hit, while Kyorge will beat Mewtwo in one hit. You're damaging the weather mons, but you're not beating them.
Mega Mewtwo Y has a chance to bea some PKyorge variants with Thunder in 2 hits and not get OHKO'd back. But again Kyorge will just switch out after the first attack.
Lastly, Solar Beam and Thunder will be useless at every point other than fighting weather leads. Luring a weather mon isn't worth wasting moveslots, especially when Psychic/Psyshock will 2HKO them as well.
In short, not a great idea. Just use a normal Mewtwo set, if you really want to lure and OHO try Z moves.