Even the ones no longer in tokens? Do all the 3 stars give covers for all 4 stars? Are there 4 stars with no corresponding 3 stars champion rewards?
I know it would take forever, especially if the 3 star was not in tokens but is it possible?
Some of the newer 4* don’t have feeders, and the Limited ones (Devil Dino and Howard) don’t either. Other than that, I think it is possible.
List of who champs to who is here, I think it’s up to date: Champion rewards [By Character] - MPQ Tips and Guides - 505 Go! Official Forums
Each 3* character only gives covers for one 4* character, and there are more characters in the 4* tier than the 3* tier. So no, you won’t get everyone.
Not to mention you only get 3 covers (one of each color) while max champing those 3’s. Forever indeed.
Most, theoretically, yes. All, no. Forever? You don’t have enough time in your life