vSphere Replication requires that the UUID source and target disks match. When restoring VMs/VMDKs with VDP, Veeam, etc., the restored disks get new UUIDs. You can manually change the UUID of each restored disk, but that is a bit cumbersome. See this FAQ for more info: vSphere Replication Frequently Asked Questions (FAQ) - The current version of this doc has moved to: https://storagehub.vmware.com/#!/vsphere-replication/vsphere-replication-faq
My question is instead of this cant you just use a VDP/Veeam backup restore it at the target site, itll be a bit out of date and point vSphere replication to that?
Not sure about SRM, but it's possible with Veeam; replica mapping is what you need here.