Previous issue: paritytech/substrate#10424

I believe it is currently possible to spam & congest a network by submitting a lot of operational transactions. They will fail but they will be included prior than normal transactions unless a sufficiently high tip is added.

This could also potentially block some critical operational transactions.

A simple solution is modify the transaction fee for any operational transaction to add a high enough base fee, and refund it if the transaction succeeds. This will raise the cost of attack via failing operational transactions.