Here's the deal. I am just now diving into actual bitcoin development myself so I could be off base in some way. I'm sure a stacker will correct me if I'm wrong :)

I've written many specs over the years but never anything open source, but you are right. I imagine it would like a lot like the current bitcoin-core dev process. In my mind it would make it easier for developers to write new clients if there were a clear spec. It would not only help with new clients but also core dev work.