Let every rarity able to level up to 130.
I don't see the point for the level difference between C/UC/R/E/L any more.
Sure, leveling up a pandaken to 130 is relatively cheap and fast, but pandaken suffers in skills and stats so it would never be as good as an epic 130 or legendary 130.
Besides, everybody gets the same chance on cheap and fast ranking monsters. For every other monster, it is going to be tough still and costly in both time/gems and food.
As it is C/UC/R/E serve very little purpose in the game and the gap between players increases exponentially with every event.
Make the game fresh again, give power potential to all the players and use the monsters already in place.