Have you thought about looking into the Cloud Connect program? This is still based on a monthly cost per protected VM. This connection then only needs TCP 443 and TCP 6180 to the service provider.
Side note: A Cloud Service Provider can create tenants and sub-tenants, so you could potentially rent space from a CSP and resell to your customers
Let me know if you want anymore information, I've just spent the last couple of weeks building out our proposition
Here's a guide for VAW to Cloud Connect if written: https://carlmcdade.com/2017/03/29/veeam ... rkstation/