I know it hasn't gotten the attention that sideboarding/best 2 of 3/banning certain cards/etc. have received as ROOT ideas, but maybe ROOT could test a mulligan rule of some sort? I came up with an idea some time back but never made a push on it.
After the initial D8, you are allowed to choose to mulligan if you want. If you do, here are the rules:
1. All LS already drawn stay in play
2. You draw 1 less card on your mulligan
3. You cannot choose who goes first, unless both players mulligan; in that case, the normal rules apply with who chooses to go first
The penalty for mulliganing is keeping your LS in play (and maybe drawing more) and drawing 1 less card. And just in case anyone would try to abuse this into generating more LS so they can guarantee that they go first, I've made a mulligan void that ability. I think this keeps it severe enough that someone will mulligan only if they have a terrible hand; that is what I ultimately wanted to accomplish. Mulligans should be rare by design. If they aren't, you are just letting players try and shoot for a perfect starting hand.
Before criticizing my idea, let's first discuss if there is even any interest in running ROOT with normal rules, with an additional mulligan rule. If there is no interest, there's no point in discussing mulligan ideas.