There's a pretty broad suite of moves that is in and of itself powerful. Thing is, these moves also have basically universal distribution. Gen 1 Mons are probably the most formidable because one of their always moves is Bide, which is why I brought that up specifically.
Otherwise Toxic, Protect, Substitute, Swagger, Rest, Sleep Talk (except Gen 5), (various Normal attacks), are defined by being strategies any Pokemon can employ. Really the Gen 5 mons get shafted the most on this aspect but the fact remains these strategies are available to every mon, and are sufficiently good moves on their own.
But that's not why I was posting, I was thinking of changing Levitate.
As it stands, Levitate Pokemon are generally disadvantaged in All Abilities battles because aside from Bronzor and Bronzong, none of them have other abilities. This proposal would instead change Levitate from an Innate ability to a Trait. Traits would be a separate ability type in that they would always be active (so basically Levitate/Truant/Slow Start).
These Traits can be Skill Swapped, but the Trait does not disappear from the Pokemon. In a One Ability Battle, a Pokemon with Levitate using Skill Swap will instead steal the opponent's ability, and Role Play will duplicate the opponent's abilities without losing Levitate.
Finally, the Levitate Trait will be applied to Pokemon that already float or fly as a matter of course. Pokemon that are low to the ground will still be hit by Seismic attacks, but these Pokemon will not. Instead they will be a subset with a Command type Levitate.
This would be the result:
Levitate:
Type: Trait
This Pokemon naturally floats above the earth when released or easily takes flight, evading Ground moves like Bulldoze, Dig, Earthquake, and Magnitude. Other Ground moves can still hit. Levitate Pokemon will retain the Levitate trait when they use Skill Swap on an enemy, and will steal the opponent's ability (The user can specify if they want a foe or ally to gain Levitate from a Skill Swap.) If a Pokemon with Levitate uses Role Play, they will copy the opponent's abilities and retain Levitate.
Pokemon with this ability: Gastly, Haunter, Gengar, Koffing, Weezing, Misdreavus, Unown, Vibrava, Flygon, Lunatone, Solrock, Baltoy, Claydol, Duskull, Chimecho, Latias, Latios, Mismagius, Chingling, Bronzor, Bronzong, Carnivine, Rotom, Uxie, Mesprit, Azelf, Cresselia, Giratina (Origin Forme), Tynamo, Eelektrik, Eelektross, Cryogonal, Hydreigon, Rebble, Bolderdash, Stratagem, Nohface.
Pokemon that have the Levitate Trait without the ability (based on anime precedent, advanced wings, etc.):
Beedrill, Venomoth, Mew, Celebi, Dustox, Shedinja, Shuppet, Beldum, Jirachi, Deoxys, Victini, Accelgor.
Levitate Command:
Pokemon with access to the Levitate Command float or rest at an altitude too low to avoid Seismic Attacks. The seismic activity disrupts their field or concentration and they will be struck unless they use this Command or Magnet Rise. In contrast to Magnet Rise, Levitate Command only lasts for three (3) actions and has an energy cost of 5.
Pokemon with the Levitate Command (Based on Anime precedent, basic wings, etc.):
Magnemite, Magneton, Geodude, Staryu, Starmie, Dragonair, Mewtwo, Heracross, Forretress, Scizor, Nincada, Nosepass, Volbeat, Illumise, Banette, Dusclops, Glalie, Metang, Metagross, Magnezone, Froslass, Probopass, Dusknoir, Garchomp, Dialga, Palkia, Darkrai, Arceus, Cottonee, Yamask, Cofagrigus, Solosis, Duosion, Reuniclus, Vanillite, Vanillish, Vanilluxe, Excavalier, Frillish, Jellicent, Litwick, Lampent, Chandelure, Druddigon, Golett, Golurk, Klink, Klang, Klinklang, Larvesta, Volcarona, Reshiram, Zekrom, Genesect.