Intended for smaller play-groups by using a 5-packs/draft, 9 cards per pack, setup.

1 rare per pack x 5 packs of 9 cards per drafter x 5 people x 2 drafts = 50 rares/packs.

Smaller pack size = 2 uncommons and 6 commons per pack. = 50x2 uncommons and 75x4 commons. This can be balanced by color with Champions printed rarity distribution. Example: There are no colorless cards printed at common. 75x4 commons means 15 (out of 22) from each color. Uncommon and rare have colorless cards and lands to help finagle the color counts to maintain balance while maintaining the ratio.

300 + 100 + 50 = 450 card cube. This accommodates up to 10 people or 5 people twice. This also allows for more rares to be incorporated without, I think, disrupting the ratio of R, U, C cards too much. With the intended method of play, you open 5 rares (vs. 3, normally). This is the most significant change to the "as close to limited" idea, but I like how it adds just a bit of spice.