I wonder if that would be a viable way for payment services to pay to protect against double spending.
If the payment processor was handling 1000 BTC every block and was willing to pay 0.1% fees, then it could create a transaction with 1BTC in fees.
If an attacker tried to double spend a transaction of 0.1BTC, then even if he was to spend the entire transaction to fees, the payment processor would be able to out bid him.
It kind of works like insurance. The payment processor combines lots of small double spend threats and protects them with a single transaction.
The processor could keep sending out a larger and large transaction (with fee) until eventually a block is found.
It requires RBF. First seen safe would be incompatible, if the double spender gets their transaction into the system first.
A 1BTC fee transaction in nearly every block would also be a boost for network security.
It avoids Peter Todd's complaint that mining pools might make secret deals with payment services. The transaction would be public and all miners could include it in their block.