Interesting,
I've automated deployment with SDNET and templates, but the other stuff you're doing with terraform is more akin "Orchestration" There must be some GUI for terraform that works with proxmox.
I guess you could do the same with expansible and playbooks but it sounds like you're looking for something with a GUI that does the work for you.
I can't think of any, but proxmox does have an API ... wondering why no one has done this yet ....