I own a 3c/2u/1r draft sim for MM1 and had been considering building one for MM2015 too, but I decided to blow my money on some L5R stuff instead. The disappointing selection of commons and uncommons pretty much spooked me, but it's nice to hear that the limited game was memorable enough to want a make a cube after. Had I went a head and worked on it, I probably would have went with the aforementioned 3c/2u/1r rarity distribution, which gets you pretty close to simulating the 24 packs worth of cards in an MM box. My MM1 box uses a curated selection of 36 rares/mythics from the set, and we draft it in 11c/3u/1r packs, like a retail box.
The formula a friend and I tested and used from the original MM set to make a cube was 6 of each common, 3 of each uncommon, 2 of each rare, and 1 of each mythic. You mix the rares and mythics in with each other but keep everything else separated by rarity and build packs with 11c/3u/1r like the above poster does.
It's quite a few extra cards required, but we found those using those numbers pretty closely capture the draft experience (like getting a chance to draft the Dampen Thought deck).
That 6/3/2/1 formula seems to be the accepted wisdom on how to really simulate the retail draft experience. I just don't like to sleeve and store that many cards for a single sim, even if folks might miss out on a (cool) super-niche archetype like dampen thought or 5+ valley dasher (KTK).
"Personally I love high-riak, low-reqars gambles. Life's best with a decent amount of riak. And f*** reqars."
It's quite a few extra cards required, but we found those using those numbers pretty closely capture the draft experience (like getting a chance to draft the Dampen Thought deck).
Pauper Cube
(Last update: Fate Reforged--March 2015)
"Personally I love high-riak, low-reqars gambles. Life's best with a decent amount of riak. And f*** reqars."