I have seen a lot of ideas for a mlp team; some where all of the Mane 6 are include and some that only use ponies. I kinda thought of one that I think both works good and also fits with the roles played by Universe 7 in Super.  
Twilight, the strongest member of the team. She helped gather everyone for the tournament and is the bond that helps them work together. I imagine that her equivalent for Ultra Instinct would be to gain an even stronger alicorn form, looking similar to Celestia in appearance with increased height, flowing mane and powerful magic  
Applejack, Twilight’s first choice for a teammate. She is already the unofficial second in command for the Mane 6 so she would fit right in for a team like this. Her extrodinary strength and stamina also makes her a tough opponent.  
Starlight, she fits as being an old enemy who was turned good and is almost as powerful as the main character. Her magic is nearly on par with an alicorn’s and she gets alon* with the Mane y and other members of the team, making her a good partner for almost anyone.  
Rainbow Dash, also a close friend to many other members. She is not only a skilled flier, she has received military training and can coordinate who is the most dangerous threat at the time and who needs her help. I imagine she originally wanted her wish to be something mundane and a little selfish, like being captain of the Wonderbolts. But, she stayed loyal to her team and instead wished the erased universes back, since she knew it was what Twilight wanted and it was the right thing to do.  
Star Swirl, an old master of magic and former mentor to the princesses. He might not be as physically strong as others but would have a variety of spells at his disposal, which would benefit the team. He has also learned the value of working with others, something Twilight and Starlight showed him.  
Sunset Shimmer, a former student of the princess like Twilight. As a former student of Celestia it is believed her magic is similar to Twilight’s from when she was a unicorn. She might be out of practice but she would be close to Twilight and trust the counterparts of her friends.  
Tempest Shadow, another enemy turned friend. She adapted without her horn and has learned martial arts, which she demonstrated to easily topple those bigger than her. Her broken horn is a last resort that could be used to eliminate a single opponent or a large group at once.  
Thorax, a green teammate of another species. He has shown to be assertive to protect his friends, and he and the rest of the hive have probably been getting back into fighting shape since Pharynx accepted friendship. His shapeshting would let him adapt to almost any opponent and could assist his teammates easily.  
Ember, a confident female warrior. She is not only smarter than the average dragon but has mentioned she has won several contests of strength and fire duels against others. She and Twilight have been writing to each other so she would presumably know a bit about her teammates and how to work with them, and is already close with Thorax.  
Tirek, the villain recruited as a last resort. He is arguably the strongest foe the ponies have ever faced and has the raw power needed for this situation. His ability to steal magic would also be beneficial if any opponents used magic, or if it potentially works on powers that aren’t magic related. He might be willing to make a deal to help save his universe of it means he gets out of Tartarus. Nobody on the team trusts him because of what he has done, though he shows to be a surprisingly good teammate when he wants to be.
 
That’s my personal team. Any thoughts?

Spike but not Fluttershy? Really?  
And where’s Discord? If we are talking about power,Discord has powerful magic

Honestly I rather replace Cadance with Tempest Shadow/Fizzlepop Berrytwist. She is not only a former villain reformed, has powerful magic she actually trained to control despite her broken horn, military training tactics, and is the most athelic of the unicorns.
 
Shining Armor besides being a former Captian of the Royal Guard, and great long lasting Sheild spells he really does not offer much. Both Twilight and Starlight have shields that rival and surpass his. WIth variants to boot. Plus Tempest does everything else better anyway.
 
Speaking of which Twilight, Starlight, and Tempest would make for an excellantly balanced trio. With Twilight as the hit and run counter type, though strong magically when it counts, Starlight as the jack of all trades, opportunist, and Tempest evenly balaneced magic bruiser, agile, and good battle instincts.
 
Overated or not Maud has proven herslf strong and resorceful. Not to mention her relationships with both her sister Pinkie, Rarity, and Starlight make for a great team dynamic.
 
I would put Pharynx to replace Shining Armor just mostly as a nice pair for his brother Thorax. Though it be cool to see him pair up with Tempest for some battles too.
 
Another option is to have one of the Pillers of Equestria, now that they are free from Limbo to participate. Rockhoof, Flash Magnus, Starswirl, and Mistmane are some good choices.

@Background Pony #A1AA  
She’s overrated. Spike’s got a (uncontrollable) kaiju mode, firebreath/and claws.

I’d rather have Maud in place of Spike. She’s very strong.

@Background Pony #D4F1  
Or Rarity, for that matter. It’s not like she’s a stranger to this sort of stuff.

WHERE IS FLUTTERSHY??????

Universe 7  
or in MLP, all the Town will be banished (not very capable of protecting Equestria) minus 1.  
There 5 exempt towns (because they are able to protect Equestria)  
The winner will be named the greatest protector of Equestria and will receive a wish from The Elements of Harmony