I would suggest changing the system that gives heroes a little. It’s a matter of luck what skills the heroes have, which is annoying because some skills are better or more useful depending on how you play.

I understand that it would be too strong if you could choose the hero skills directly (you could otherwise introduce this as an option for the campaign, similar to turning off the round limit, etc.)
my proposition:
The game randomly chooses three hero skills and the player then has to choose one. That would not be as strong as if you could choose from all abilities yourself, but you do not have the problem of getting a “useless” hero because he does not fit the style of play etc. (clearly you can be extremely unlucky and get three “useless” abilities, but that’s unlikely)

New ability as a commander: “An eye for skills” (or talent) (costs 2 points)
After each mission, you can choose from 5 (or 4) heroes instead of just 3.

New weakness: “To self-confident” / “Proud selfish” (gives a point)
You can only choose from 2 heroes instead of 3.
(Logically, strength and weakness cannot both be taken)

Think that would be a sensible middle way between “100% diceroll” and “choose your skills from the whole list”.