This is the team from my second successful playthrough of Shield. To my knowledge, everything on this team is accessible in Sword, so you don't have to worry about making substitutions. This team focuses on two big things-type coverage, and hitting everything as hard as possible. There are a few setup moves, but you may not find yourself using them very often. I'll put in the natures I got, the items I gave them, and, just for fun, their nicknames.
Bubble 07 the Inteleon
Received as Sobble in Postwick
U-Turn (level 30 as Drizzile)
Snipe Shot (learned upon evolution)
Ice Beam (TR05)
Tearful Look (level 19 as Drizzile)
Sobble is your primary special attacker, though its Attack stat isn't too shabby either. It's fast, it hits hard, it learns some pretty great moves, what's not to like? Snipe Shot is Inteleon's signature move, with high Base Power and STAB, and while there are options with higher Base Power, it works well enough for the main story. Up until your starter learns Snipe Shot, I'd recommend using Water Pulse. U-Turn is mostly in case things get dicey and you need a free switch, but it can be used to deal with Piers and Marnie. Ice Beam gives you a massive advantage if you can get your hands on it, and hits for decent neutral or super-effective damage on most things. Tearful Look is filler, as I couldn't think of anything else to add, but it at least reduces the opponent's Attack.
Nevermore the Corviknight
Caught as Rookidee on Route 1
Brave Bird (level 50)
Steel Wing (learned upon evolution
Revenge (TM found in Ballonlea)
Hone Claws (level 8 as Rookidee)
If I had to describe Corviknight in a word, I would say-BULKY. Its Steel typing negates the Ice weakness from its Flying typing, it resists nearly everything, and its Defense and HP are high enough that it can usually tank a couple of super-effective hits. Brave Bird is Flying STAB and hits hard, at the expense of some HP. Steel Wing is Steel STAB, Revenge is coverage for Ice- and Dark-types, and Hone Claws makes Corviknight hit harder.
Roxie the Obstagoon
Caught as Zigzagoon on Route 2
Thunder Punch (TM Shop in Wyndon)
Night Slash (level 30 as Linoone)
Obstruct (learned upon evolution)
Shadow Claw (TM found at the Lake of Outrage)
Obstagoon will be your main physical attacker. It's a bit like Inteleon in that it's fast and hits hard. It's also immune to Ghost-Types, so that's neat. Thunder Punch is there to take out Flying- and Water-types if you can't use Roserade for some reason, but it'll hit for pretty good neutral damage on a lot of things. Night Slash is Dark STAB, and utterly demolishes Ghost-Types (like Allister's team) and Psychic-Types, of which there seems to be an abundance. Obstruct is just to be annoying and keep the opponent from doing anything. Shadow Claw is general coverage.
Haru the Roserade
Caught as Roselia in Rolling Fields
Toxic (level 40 as Roselia)
Giga Drain (level 30 as Roselia)
Synthesis (level 35 as Roselia)
Venoshock (TM found in Stow-on-Side)
Do you want to just breeze through the first half of the game? Of course you do. Just catch the Roselia in Rolling Fields and you can pretty much cheese your way through the first five Gyms. Roserade is your secondary special attacker. She's a bit bulkier than Inteleon, and hits just as hard. Toxic badly poisons the opponent, and powers up Venoshock. Giga Drain is Grass STAB and restores HP. Synthesis keeps Roserade in the fight longer and keeps you from having to use a healing item.
Kyubey the Sylveon
Caught as Eevee on Route 4
Moonblast (level 50)
Sunny Day (TM Shop in Hammerlocke)
Last Resort (level 55)
This one and the next one are mainly here to handle what the others can't deal with. Sylveon is slow, but he can take a lot of hits and do a lot of damage, he's immune to Dragon-types, and he can act as a support 'Mon if need be. Moonblast is Fairy STAB, and your answer to Leon's Dragapult and Haxorus. Psyshock is coverage for Poison-Types. Sunny Day is to help the others, as it lets Roserade heal even more with Synthesis, and powers up Flygon's Flamethrower and lets it use Solar Beam without having to charge.
And last, but not least...
Sandy the Flygon
Caught as Trapinch in a Max Raid Battle
Earthquake (level 44 as Vibrava)
Solar Beam (TM found in Turffield)
Dragon Claw (learned upon evolution)
FLYGON OP PLEASE NERF. Even as a Trapinch, she was destroying everything in her path. I was supremely lucky to find one before Route 6, but if you can't find one as early, you should still do fine until then. She'll be your mixed attacker, even though her Special Attack isn't quite as good as her Attack. Her stats are good all-around, and she has a surprisingly diverse moveset. Earthquake is Ground STAB, and will pretty much 1HKO or 2HKO everything. Solar Beam is just in case things get ugly and you need to hit really hard. It should be used in tandem with Sylveon's Sunny Day. Dragon Claw is Dragon STAB. Flamethrower is coverage for Ice-Types.