I think it'd be cool if A+ dragons got some sort of benefit for continuing to win battles. It could be something really small and require 100 extra battles to gain, but after 250 wins there is no increase in anything. Maybe an A+++

I think a max is good. But you could add a rank S which is usually max in other games. For continuing to win I think food is a better option

I'd be good with food as an option too. Can never have enough food!

@arcdarksmurf perhaps the S rank could be platinum since C is bronze, B is silver, and A is gold