If the customer buy's a Veeam License you could replicate customers VM's to your location or Schedule a backup job to store the data @ your location.
(using VPN tunnel, ISCSI Storage @ your site etc.)
Width ISCSI you can bring up unique LUN's for each customer.
Although i would recommend at least 10Mbps internet Connection @ customer site, and 100Mbps Connection at your site.(depending of how many customer jobs run @ the same time)