Rarity Matters = ‘Hierarchy’
Consider that 60 cards is same amount as four 15-card booster packs. Then consider the rarity of the cards you’ll get from opening those fresh packs.
With four packs, you get 1 mythic, 3 rares, 12 uncommons, and the rest commons. These new rules similarly restricts deck building by following the same ratios for a minimum 60-card deck. A deck can have any amount of commons and Basic Lands.
Additional rule: no more than three (3) copies of any card except Basic Lands.
Each additional 15 cards in your deck beyond 60 cards grants another 1 rare and 3 uncommons. For each additional 60 cards of your deck size, you may include a mythic instead of a rare.
You can trade from higher rarity for same ratio of lower rarity, or vice versa. That means you can omit 1 mythic for 3 more rares or 12 uncommons. Omit 1 rare to add 3 more uncommons. In reverse, you can trade in 3 uncommons for 1 rare or 12 uncommons for 1 mythic. Likewise, trade 3 rares for 1 mythic. Fill vacancies with commons or basics.
A card’s rarity is based on its latest printing in a core, expansion, or draftable set that are legal for that format. This includes supplemental draftable products like conspiracy and masters.
These rules can be applied to official and unofficial formats. So you can have Hierarchy Standard and Hierarchy Modern, etc.