requires a tiny amount of skill and costs something like 0.2 hive to play

That would be great but is very hard to accomplish.
Both the skill factor and the cost to play.

If the game requires skill how does one stop cheaters from botting it and other Sybil attacks?

If the game requires an entry fee who's going to hold the money in escrow and then pay the winner? That entity is guilty of running an unregulated gambling ring. How does this get navigated? 'Decentralized' in this context often means a bigger group is simply breaking the law... any very few gambling solutions are actually decentrailized beyond multisig... which again is just a couple more people being in on it and not a real solution.