Make them passively charge to max rather than having to hold the trigger down.
This will be no different to someone who manually holds the trigger down whenever they dont have a target, it just saves peoples trigger finger from having to constantly be pressed down. you could still fire before getting max charge just like now.
This change wouldnt affect the weapons stats or power in anyway, it would just make it less likely to cause hand cramp or other hand issues, especially on PC its awkward/annoying to hold the charge on