What perks would you want to see returning?

[Stop Mocking Me0]

That doesn't improve your chances of getting it, it gives you more chances to get it. Furthermore:

 Cheap. 

Perkaholic is designed to be used once in a blue moon when you really want to go tryhard, a more common gumball would be helpful for more in-game revives. 
Not to mention there should be a gum that actually helps players more in solo then co-op, always found something annoying about this.