Welcome, my collection of cubes are mainly paper based block cubes. I in general design the cubes using all cards in certain blocks and refrain from singleton in order to make them work in the environment with the same feeling as the sanctioned draft format. Typically, I calculate the expected mana curve as well as expected creature ratio of the sanctioned format and try to follow that in the cubes. The result is a draft environment with the same feeling as the limited booster format but with a higher power level.
Enjoy!