My employer uses third-party payment gateways to process debit and credit card payments on our website. Until recently, including these in GA's Referral Exclusion list has been adequate to make sure the transaction is attributed to the last click instead of the gateway as a Referral. There have been very few changes in two years so it hasn't been a big problem.
Now my employer wants to use the Barclaycard Smartpay gateway because of more competitive charges. This uses Verified by Visa for some transactions. Customers reach the payment stage, are shown a Barclaycard gateway and on completing that they possibly see a Verified by Visa gateway on a subdomain belonging to another bank. All these are counted as Referrals if not excluded - in other words there will be a Referral from the domain belonging to the bank doing the Verified by Visa. The de facto standard advice is to add payment gateway domains to the Referral Exlcusion list. But there are two problems here.
First, there are at least three Barclaycard gateways. OK, this isn't insurmountable and perhaps we can get a full list from Barclaycard. The larger problem is the Verified by Visa gateways. We can't predict these and would have to keep an eye on Referral traffic to find new ones (assuming we could infer what they are).
Is there a more elegant and 'future-proof' solution than adding domains to the Referral Exclusion list?