Is it possible and convenient to address a small fee to the Dev wallet when a smart contract between 2 counterparts has been cleared?
If you're looking to make a return from users of your smart contract, you could take a percentage from a transaction to the contract and sends it to another address. It gets a little weird with percents, because as far as I know (I'd love to hear otherwise) fixed point types are still in development.
You could write in a basic fee condition. Say you have a
payable function in the contract that would otherwise only require gas to call. In Solidity, you could just call
msg.value within the function to get the amount sent, and
throw if the amount sent to the contract is less than the fee.
But even if you had something in your contract or Dapp that charged a fee, the contract is still viewable by anyone on the public blockchain. Meaning, with enough effort someone could reverse-engineer the contract and create a new one without the fee.