The first answer is yes, there is a Blueprint method called GetCooldown which you can override with whatever logic you want. You can use GetBaseCooldown to return the value you have set on the Ability itself, then check stats/logic/whatever on how you want to modify that value.
The second answer is no, but you could create a quick load version and just have some logic that says “If I have this buff/stat/whatever, then play the quick reload - otherwise play the normal reload”. I can look at making that more dynamic in the meantime.