Other I think about "XP Feedback Mechanism"

[Bannou Neko]

I don't use characters for power up, only for evolve, and I try to get many Skill Points as I can.
In Prize Fight (gold), I usually use 1~2 Max Lvl of Gold or Diamond to carry low Lvl characters depend on longshot or streak. It take lots of time(8~10hrs/day)!, and Max Lvl characters will waste lots XP
I think, it might be have a way to recycle those XP for power up non-Max Lvl characters.

I try not to broken the power up system, and this is my Concept of "XP Feedback Mechanism"

Example:
Use Max Lvl Silver character(1) on Prize Fight Earn 10XP, 3 Max Lvl Gold you get total 30XP
Use Max Lvl Silver character(1) on Prize Fight Earn 30XP, 3 Max Lvl Gold you get total 90XP
Use Max Lvl Gold character(1) on Prize Fight Earn 50XP, 3 Max Lvl Gold you get total 150XP
Use Max Lvl Diamonds character(1) on Prize Fight Earn 80XP, 3 Max Lvl Diamonds you get total 240XP
When XP reach to 10,000XP it can be turn into a "Pure Soul(whatever) Item" for Bronze/Silver Characters Only

When player unlock the Prize Fight also unlock XP feedback mechanism
the reason this XP item can't use on Gold / Diamonds
* Helps new player to lvl up lower character faster and get more Skill Points
* Player should Work on Gold / Diamond character, learning how to attack / defense and fighting combos

P.S. I also consider this on Daily Events and Story, but it will get too many problems. Different difficulty XP, first time finish XP/ redo stage XP...etc