Decentralised hashpower marketplace

Is it possible to use ETH functionality to create a decentralised hashpower marketplace? It could be ETH itself that is to be mined but it could also be other ERC20 coins.

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And one crazy step further, could it be made possible to 51% attack a coin with smaller market cap than ETH using such a marketplace? Basically everyone locks some collateral and contributes hashpower and in return also gets to specify transactions they wish to double spend. If the attack is successful, a formula is used to calculate rewards. If it fails too calculation happens and people get back their collaterals back. Note that these collaterals are in addition to whatever coins are being mined. It is possible to evaluate entire blockchains inside a smart contract as far as I know. Note that this pool of colluders will not necessarily accept everyone, for instance if X pays Y pays Z on the honest chain and X wishes to double spend, X can't let Y and Z join this attack since they could just reverse attack him back. So either we let the person with more money in, or its first come first serve, or some other formula

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Solutions involving ZKPs or rollups are welcome too. Also I'm ignoring the part about many coins not being profitable to 51% attack (value of coins goes down) but looking at the recent 51% attacks on ETC (and no consequent impact on price), it could still be worth the risk