You are on the right track.
Below is a recipe for "grouped heroes" I got acquainted with years ago. Take what you need and leave the rest.
What you want is:
a)
Stakes that will last the entire story. (Cut & Paste from
link ) If at any point your Heroine has the option to call it quits, then the stakes are not high enough. One way to achieve this is to have a Death Threat(tm) of some kind, which can be sub-divided as:
Threat of physical death - the bread & butter of most thrillers out there.
Threat of emotional death - losing love or respect from a close relative (ex: Leslie Lehr - What A Mother Knows)
Threat of economic death - losing a fortune, the family company (ex: Largo Winch)
Threat of social death - losing status, a career, being framed. (ex: Michael Crichton - A Case Of Need)
Threat of psychological death - losing honor, feeling empty, falling into eternal sorrow, revenge. (ex: Josin McQueln - Premeditated)
You are golden if you can mix two or more along your storyline.
You are doubly golden if each Hero has a different threat for the same problem.
Ex: Group Heroes must find a kidnapped kid.
Hero # 1 is secretly in love with kidnapped kid.
Hero # 2 : kid was kidnapped while using Hero # 3's motorbike. Bike is nowhere to be found. Parent are coming back from Mexico in a week.
Hero # 3 want to prove the older brother he/she is not a Loser (with a big L) by helping find the kidnapped kid.
etc.
b)
A set of weaknesses that are personal and social. A good mix of both will usually do the trick. Make the social weaknesses at the core of the conflicts between your main characters. Make the physical weaknesses the main weapons of the Opponent.
Ex:
Hero #1 is physically weak (P) and questions every group decision (S).
Hero # 2 is afraid of the dark (P) and a pedant know-it-all (S).
Hero # 3 stutters (P) and is a defeatist (S)
etc.
c)
A set of intertwined redeeming qualities. There has to be something for which - as a group - is the only way to defeat the Opponent(s) but taken individually will cause them to have many setbacks.
Ex:
Hero # 1 is a hacker.
Hero # 2 can pick locks.
Hero # 3 is an acrobat.
As an exercise, you may want to pick apart the characters in The Avengers: Infinity Wars along the template above and see what you get. As a second exercise, try The Magnificent Seven.
Hope this helps.
-cb