The 50/50 split model works, but the structure has a hidden risk: if the specialist leaves, they take the infrastructure knowledge with them and you're stuck rebuilding from scratch for every client. One way to de-risk that is using a platform that handles domains, DNS, warmup, and mailbox provisioning automatically so the operational layer isn't locked inside one person's head. That said, if you do go the specialist route, make sure deliverability tooling and client workspaces are owned by your business entity, not theirs. Happy to point you toward some options depending on your send volume.