I think the optimal game design should not have BC boosters, they are failed idea of just additional cash grab. The coins should come from normal missions and just playing a game (at reasonable rate).
Evolution of AW BP - instead of normal rewards we get more and more boosters, where each booster gives less and less coins per level, instead the cost of single level grows over last BP. I still have more than 20 boosters.
Once I passed final missions with 8K for type 10 skin, I lost any further interest to play BP. Not having any commander with some new interesting mechanics is failure. Type 10 is shiny power-creeped piece, but in 6-8 it will be there where Altay.
Probably biggest mistake now is to open weekly SO containers. They theoretically should be open in the time of new BP, with a new "valid" coins.