What would a champion with two resource bars look like?

Quick question: Why would I ever need two ressources in the first place ?

Their bars would look vaguely like Jhin, but if you mean their abilities use 2 different resources then look no further than Banana Master 's W

I was thinking of a concept but quickly realized it's what the WoW balance druid is.

One bar, two resources. Using one resource adds that amount equally to the other side (total of both is always 100). The more of the type you have the stronger the effects from using it are.

Maybe the Ultimate can switch your stance so you have 3 spells for each resource. The Ultimate has a short CD, maybe 10-15 seconds. Your resource bar balances towards 50% over time, so you can either swap stances and use your other abilities when you run out of the resource you're on, or you can wait a little bit to get more and use your abilities.