So the idea is that some people could wind up using these machines as their dev boxes and just deleting the machines wouldn't be a good thing, especially if they had stuff on there that needed be saved.
Understand, and this is a common theme which comes up with many customers. The solution to this is often a difficult to swallow. It's a problem of people and process. People shouldn't be doing things on machines for which the catalog wasn't designed. This is a personnel and managerial problem which requires some training and education. The process problem comes in when allowing devs to save code locally, which isn't good dev practices anyhow. This is precisely why version control and source repos exist. Again, it's a combination of both. vRA and what it enables (private/hybrid cloud) means a different operational model, and that means it can't be contorted into a pretty web front end for vCenter. Trying to make it so without modifying any of your processes and tooling inevitably doesn't go well.
but if there was a way to automatically send out a renewal notice to users as well then I could probably live with that
Well, this happens automatically today. 7 days prior to lease expiration, the owner gets an email saying their machine is about to expire. The email will have a subject called The lease of Deployment "<Deployment_Name_Here" will expire soon.