How can we allow Commerce 2 users with a role to bypass (pay later) payment during the payment process?

We have a Commerce 2 site where we can assign a role to users ("Bill Me Later"), through which the user can select the payment option "Bill Me Later" during the payment process.

I have not found a module that provides this functionality. I started to work on creating a custom payment processor, but I'm not sure if this is the way to go. If the user selected "Bill Me Later", no further information would be required. The order would go through (completed), but now marked as paid.

Could someone give an insight into the best way to achieve this? We are open to creating a custom payment gateway module, if necessary, but could use a few startup instructions as it is not technically a payment gateway.