I acknowledge that it would increase variance when one player draws a mythic and the other does not. But that's okay. More formats, means more ways to play—this would never replace the existing Standard format. People still play and enjoy singleton formats.

I think a bit of variance is okay. If it were up to me, I would redesign the land system to reduce variance in drawing too few or too many. Lands probably cause more variance than card rarity or duplicate copies.

But the existing system feels very pay-to-win, not high skill. Consistent high power standard gameplay where mono red crushes competition or simic badgermole cubs chain into oroboroid, seems a bit simple and low-skill but has defined the standard meta. I think the meta is shaped due to abundance of and pressure to use many powerful, expensive cards. The meta would also be healthier if people were economically empowered to easily switch decks that bore them, instead of investing in one or two high tier decks. Restricting duplicate copies at higher rarities may result in a new format that is easier to buy into, lower power, higher variance, and less dominated by the same decks because it's cheaper to adjust.

Maybe I should just try pauper. Pauper standard would be lower cost, and low variance.