A balanced and considered change to Legion
So the potential of Legion, especially with Stab Wounds/Mixtape is very high. So although she (i'm saying she because Susie is best Legion, and should be default.) Is the frequency and recovery of her power. Using her power not fully charge is incredibly painful, and normally will see her sprint forwards, and then impotently gas out after a few feet, with the survivor just sprinting away laughing. This especially gets frustrating when trying to track multiple survivors. (Like say hookswarming, or trying to heal a downed player) In that they can easily exploit this, especially with Sprint-based perks.
The change that I think would make this better, and result in Legion feel better in general, and a lot less stop-starty, leading to less stuns in general. (because taking a stun hit 30 times a game watching survivors run away/teabag is just not rewarding gameplay.) would be to reduce the cooldown considerably, to around 7 seconds or so, letting you use it for a decent duration quickly, and making the sprint more viable for map control. The tradeoff would be to restrict using the ability untill it is fully charged, it would still regen from where it was left if you only used it a few seconds, but the meter would need to be full before the power can be activated (Just in the same way Spirits power works), this would both make Legion a bit smoother, more fun, and should be enough to leave them in a good place balance wise.