I had a similar idea and thus second your idea.
But when we look at the time, there is a difference between the transaction time and the time it takes to be sure that the transaction is legitimate and thus will stay in the ledger.
This video: https://www.youtube.com/watch?v=fBKCbhX-dXI&feature=youtu.be&t=1550 says Cardano handles (an average of) 257 transactions per second.
This link says that it takes 5 minutes to be resonable sure that the transaction is legitime.
But basically: the longer you wait (more confirmations) the more certain the transaction will remain.
I attended this meetup and it was my understanding that you can be sure 99% after 20 minutes and 99,9999999999999etc after 12 hours.
But to get back to the topic.
If a customer walkes into a store and pays something with Ada. How long does the seller have to wait until he is sure he gets the Ada/money? And thus how long until the customer may leave the store? Waiting minutes to buy a car could be ok, but waiting minutes after paying at MacDonalds is not really an option in real life.
A credit card transaction gives the seller a authorization-approval-code, so he is sure that he will get his money.
Maybe Cardano can make a payment Insurance DApp or smart contract where the seller will get a confirmation within seconds and does not have to wait x minutes to be sure that he will get his Ada/money.
Maybe Cardano could setup some automated insurance agents with a starting insurance capital. Whenever someone uses this service the automated insurance agents will get x% (less than 1%) of the transaction, because he takes the risk.
Maybe they can start with insuring small transactions like up to $100. So that the general public can grow trust in the Cardano system.
If the system is abused or when there is a (temporary) unresolved hack/flaw, then just (temporarily) don’t insure any new transactions until the problem is fixed.
Maybe make a system where commercial companies can enter the market and insure transactions at their own rate. Each transaction could be offered to the network and the first one to accept (and the cheapet within x seconds) will get the deal.
Is that something which Cardano is looking in to?