I think part of the confusion here is that Visa's role in fraud detection / prevention is not well understood.
Issuing banks are the entity (in the US at least) that know about the cardholder.
The merchant bank is the entity that the merchant runs cards through.
Visa connects the merchant bank to issuing banks. You'll notice that Visa already uses different rates to govern fees assessed on a merchant banks' transaction with an issuing bank based on details about how the transaction occurs, and where:
https://usa.visa.com/dam/VCOM/download/merchants/visa-usa-in...
You'll notice nothing relating to chargebacks per se; the assumption being higher risk transactions are more likely to be refunded or canceled, so each one "costs" more for the merchant bank to issue in the first place.
The merchant bank sets the rate for the business type based on the fees it expects to pay for the transaction mix the merchant will bring.
Merchant banks will almost always roll on an issuing bank requesting a charge back from a customer because customer retention is their highest priority (because you can charge the consumer interest), whereas the merchant knows it's a pain in the ass or existential to stop using them and switch to another processor, so they know you'll eat it.
The merchant bank has a lot less to lose than the issuer bank, so it's not like they're going to go to bat.
Visa does govern the agreements between Merchants and Issuers using their services, and they get to decide certain features of Issuer's cards with Visa logo trademarks. But they can't tell them how to run their fraud operations, for example.
That's why Visa doesn't really enter into the equation here.