I'm not sure if this is what mmitche intended, but in my case I'd find it very valuable to be able to bind existing Jenkins credentials (aka "secrets" – username/password, secret text, etc.) and use them within the initialization scripts. For example, when I provision my Windows agents, I need to establish a NuGet source that requires a username and password, and currently that password must be hard-coded into every initialization script field (for each template that needs it).
mmitche could give more details about this request?