Hi Andy,
Nick here from Shopify.
This is a really good question, but it’s not something which would be possible. The reason being is because the payment gateways apply to the checkout and not products themselves. I think your best chance for a workaround with this would be a split payment app. You can see some of the most popular split payment apps below:
I know this isn’t an exact solution but due to how the system is built it’s just not possible to do this natively. Hopefully, you can find a way within the split payment apps for it to work.
Don’t hesitate to ask should you have any other questions.
All the best, Nick