It seems like common sense. Give players a trickle of keys and crates... but allow them to pay for more keys whenever they want. Done exclude completely. I hate to say this but... Look at how 3Arc handled the BLOPS3 Crates. As much as i detest it in that game i'd love it in this game! (save for them hiding truly unique, new cars in crates... not just re-skins)
We'll see how this developes over time.