I would like to see multiple crates. Each crate consumes more keys the better the loot inside. For instance;
Crate 1 could cost 1 key, and be filled with more common blocks and or collectibles.
Crate 2 could cost 5 keys, and be filled with skulkers full of rare blocks such as; obby, iron, etc.
Crate 3 could cost 10-20 keys and be filled with Very rare blocks and or a spawner, (something simple, cow, chicken, pig,) (not a villager, pigman, iron golem) and or diamonds, emeralds, gold, iron, and heads. You could also put the rare collectibles in this one so they are harder to get.