Catchy title, eh?
Damage bubbles can be purchased for 4k cr each per punching bag and upkeep is 500cr per. This only applies to GTH. Damage bubbles will display the last amount of damage dealt in a small bubble above the punching bag affected. This will allow you to screenshot your damage dealt. Not much, but I think it'd be fun and useful. Sometimes the numbers disappear too quickly for me. Bubbles would disappear after 30 sec or so.
Going even further it could show something like dps if upgraded. But that's more of a side thought than serious.
Personally, I'd rather have all the damage data laid out for everyone already. Having to judge by vague bars and various tests isn't very intuitive.
Ex:
Hammer
||||||||||||||||| Elemental
would become
First hit: X
Second hit: Y x 3
Third hit: Z
Charge attack: W x 2