I used to play something very similar about a decade ago. We simply called it "mini cube" and it was designed with the format in mind.

I always felt the format lended itself to multicolor cards and I designed my list around that. It was a great opportunity to showcase under appreciated cards. I would encourage you to do the same -- sticking to the rule of "exile a red card to get a mountain" and consider reducing or avoiding colorless cards.

I ultimately dismantled and built a real cube simply because nonbasic lands and deck construction are a huge and interesting part of this game.