Again, even if a single user in the pool theoretically has the power to unilaterally withdraw their funds, if it is cost-prohibitive then it might as well not exist as an option.
There's a cost for everything. Perhaps there could be a mechanism, wherein the user who closes the channel / pool pays most, but there will always be a cost. If you increased the block size, the fee rate would surely drop, but the cost would later be translated in decentralization.
If I'm keeping my life savings of 100,000 sats in a CoinPool, and the transaction cost is 50,000 sats, then the option to withdraw my funds unilaterally basically doesn't exist.
You talk with numbers, but there's no indication that you will pay 50,000 sats for an on-chain transaction.