I playtested it a little bit and can say, that it holds up very well in mid-power games. The gameplan consists of searching and protecting Krark's Thumb and winning off of commander damage from Okaun. So ways of giving Okaun Trample or some other form of evasion are a high priority, to get him through.

Sakashima of a Thousand Faces is a great addition, I think. Your commanders are your most reliable source of coin flips after all.

These coin flip deck tips should help you out also:

I use dice instead of coins. I roll multiple dice at a time.

I use a dice tray to keep them from going all over the place / falling down the table.

I have a cheat sheet on the table for everyone to read so that I don't have to remind everyone what I am rolling for every time (Odds / Tail / Lose - mana crypt damage, krark return spell to hand; Even / heads / Win - krark copy spell, okaun double power, zndrsplt draw a card)

On the side of the cheat sheet is the power of Okaun for every win so I don't need to compute every time: 3, 6, 12, 24, 48, 96, 192, 384, 768, 1536, 3072, 6144. At some point you can stop flipping/rolling because it will be lethal damage already. But that's the point of the deck - it's fun to roll dice. 3072 was the highest I've gotten so far.