There's no loophole, you can use your ETH while also using WETH. When you're converiting ETH into WETH, you are essentially creating a new token that is tied to the value of ETH. So you can still use your original ETH while also using WETH. You can convert your ETH to WETH and back as needed. The original ETH will be locked up in the smart contract until you decide to convert.

>What happens to the original ETH token?

When a wrapped token is created, the original cryptocurrency that is being represented is locked up in a smart contract on the new blockchain. This smart contract ensures that for every wrapped token that is created, the underlying cryptocurrency is held in reserve. When someone wants to convert their wrapped token back into the original cryptocurrency, the smart contract will release the corresponding amount of the original cryptocurrency to them. The original token is not destroyed or affected in any way during this process.