Generally speaking, it's not a good idea to swap out team members in a Pokémon game nearing the end of a playthrough. By this point of the game, your team should already be high enough level and well-composed to take on what Area Zero has to offer. Regardless, here are a list of Pokémon obtainable with good coverage, at relatively high levels, at this point of the game. Note that I'll be aiming for Pokémon around level 50 or higher, as the highest level Pokémon you'll be facing at this point of the game is level 67.
Tera Fighting Raichu can be found at the North Paldean Sea at level 60, already knowing Focus Blast, Surf, and Grass Knot. If you'd like different coverage moves, it gets Iron Tail from the Move Relearner and Trailblaze, Dig, Play Rough, and Brick Break from TM.
Slowbro can be found at Casseroya Lake at level 55 as a Tera Grass fixed encounter, already knowing Grass Knot. It gets Ice Beam, Focus Blast, Foul Play, Shadow Ball, and Flamethrower from TM.
Tera Dragon Gyarados can be found at Casseroya Lake at Level 55. It already has Ice Fang and Outrage learnt, can learn Crunch from the Move Relearner, as well as Earthquake, Stone Edge, and Iron Head from TM.
Tera Steel Dragonite can be found at level 75 in North Province (Area Two), already knowing Iron Head and Earthquake. it is also a fixed encounter in Casseroya Lake, found at level 60. It learns Thunder Punch, Fire Punch, and Aqua Tail from level up, as well as Brick Break, Stone Edge, Earthquake, Ice Punch, and Waterfall from TM.
Tera Fairy Azumarill is a fixed encounter at Casseroya Lake at level 55. It gets Bounce and Superpower from the Move Relearner, along with Trailblaze, Ice Spinner, Brick Break, and Bulldoze from TM, and learns Lash Out, High Horsepower, and Zen Headbutt through TM.
Garchomp is obtainable at level 57-58 atop the Great Crater of Paldea as a fixed encounter. It can learn Crunch through the move reminder, and moves such as Fire Fang, Thunder Fang, Aerial Ace, Brick Break, Shadow Claw, Poison Jab, Stone Edge, and more through TM. Tera Water Garchomp can also be found at level 65 at West Province (Area Two), knowing Liquidation and Rock Tomb already.
Lucario is obtainable as a Tera Ice fixed encounter at level 75 at the Dalizapa Passage. It has Ice Punch when caught, learns Bone Rush and Dragon Pulse through the move reminder, and Earthquake, Stone Edge, Psychic, Shadow Ball, Thunder Punch, Shadow Claw, Zen Headbutt, Poison Jab, and plenty of others.
Eelektross is a Tera Dragon fixed encounter at the North Paldean Sea at level 65. It learns Dragon Claw when caught, and learns Acrobatics, Zen Headbutt, Brick Break, Fire Punch, Drain Punch, Crunch, Liquidation, Giga Drain, Flamethrower, and plenty more.
Braviary is a fixed encounter at level 56-57 at the Asado Desert. It can learn Superpower through the move reminder, and Close Combat, Rock Slide, Iron Head, Zen Headbutt, Shadow Claw, Zen Headbutt, and U-Turn through TM.
Tsareena is a Tera Psychic fixed encounter at Socarrat Trail at level 65. It learns High Jump Kick from the Move Reminder, is caught with Zen Headbutt, and can learn Acrobatics, U-Turn, and Play Rough from TM.
Mimikyu is a Tera Fairy fixed encounter at North Province (Area Two) at level 65. It gets Wood Hammer from the Move Reminder and Trailblaze, Drain Punch, and Leech Life from TM.
Corviknight is a Tera Fighting fixed encounter at North Province (Area Two) at level 55. It's found with Body Press, and can learn U-Turn from TM.
Drednaw can be found at Casseroya Lake at level 55 as a Tera Ice fixed encounter, already knowing Ice Fang, Crunch, and Stomping Tantrum. It gets Poison Jab, Ice Spinner, and Earthquake from TM.
Though not the greatest for a playthrough, Wugtrio is a Tera Ground fixed encounter at North Province (Area One) at level 60. It's found with Foul Play and Stomping Tantrum, though can learn Throat Chop through the Move Reminder.
Tera Fire Revavroom is a fixed encounter at Glaseado Mountain at level 55. It's found with Overheat, and learns Lash Out, High Horsepower, and Zen Headbutt through TM.
While all these Pokémon serve as solid enough playthrough Pokémon, if you intend to cruise through Area Zero with ease, you might as well use the overleveled Dragonite and Lucario available in the wild.
