Granamyr, oldest and wisest of Dragons, and among the most powerful magic users out there http://he-man.wikia.com/wiki/Granamyr
She-Ra: someone to help keep Granamyr from getting too angry with humans, and powerful and versatile in her own right
Yoda: need the psychic force powers and precognition, and he can take care of himself
great brute force kinda guy
Ang the Avatar https://comicvine.gamespot.com/aang/4005-47646/
Rand Al Thor, with cleansed Saidar from the Wheel of Time https://comicvine.gamespot.com/rand-althor/4005-57750/
Flashback from the Silverhawks http://silverhawks.wikia.com/wiki/Flashback_
Tech guy that doesn't go on missions, but monitors from headquarters:
Gyro Gearloose http://disney.wikia.com/wiki/Gyro_Gearloose
he's most known for creating the Gizmoduck suit, but has also created spaceships, time machines, etc.
I think that works.
DC and Marvel are more difficult...if you don't want to have the same team as everyone else
You can't really have their best without Superman, WW, and Batman, but I'm going to try, meaning the first pick has to be either Orion or Captain Marvel...even though CM is Supes equal powerwise, I think you miss out on too much leadership and such, so I'm going with Orion...at least you get a mother box, boom tubes, and Astro Force...but then Orion and Barda as standins for Superman and WW...can't do that, so Barda is out...
Maxima: another good, versatile, powerful pick with solid psi
Captain Atom: I like the classic version with metallic skin...
Ray Palmer: I debated between him and Mr. Terrific, but went with Ray as the tech guy
Jason Blood: magic representative on the team, an if things get nasty
he can call on Etrigan
Will Peyton Starman - because I like the character, and he's versatile while reasonably powerful
Andrew Bennett (I...Vampire)- again, because I like him https://en.wikipedia.org/wiki/I%E2%80%A6Vampire
he has some telepathy so fortifies the lack of psi on the team
OK, the obvious three are really Surfer, Adam Warlock and Dr. Strange, probably followed by Reed Richards...I might still pick one of them, but I'm trying to not have all the obvious picks...so I'll actually go with a pick out of time....pulling characters from across Marvels timeline....
Captain Mar-Vell...not as powerful as many, but one of the best at punching out of his weight class in the MU, with awesome leadership and good cosmic awareness
Classic Drax: if we didn't know he was explicitly powered up after his death, we'd probably consider him Thor level...awesome feats, great fights with classic Thanos, very skilled and canny warrior
Quasar: Wendel. He became skilled and knowledgeable, had some very good showings as well.
Makkari, pre speedup. Post speedup he was MUCH faster, but lost most of his other eternal powers...I want eternal versatility. His relationship as Quasars roommate and friend makes this a good match.
Sersi: high end psi, matter rearrangement, etc. Also some of the best showings of any Avenger when she was on the team.
Professor Hulk: acts as the tech guy and a physical powerhouse. If you want to move away from the 'real' Hulk, you could substitute Amadeus Cho
If you pull from alternate MU realities,
Bravado (son of Thor and the Enchantress, can't use Mjolnir, but powerful magic user and class 70-90 strength)
Mach V: adequate tech guy if not top tier