GitHub doesn’t reveal how to communicate with Copilot. So, by an “official” one, you should ask GitHub to implement a ST plugin. In that case, people has been asked for you and their answer is “we would consider that”. That just means it’s not rejected and that’s all. And almost 1 year after that answer, we, the community created LSP-copilot. https://github.com/orgs/community/discussions/6617
Fwiw, the official one careted by GitHub staff for VIM uses LSP protocol. And hence LSP-copilot utilize that too without caring about more low-level implementation details.
The only way to get rid of LSP is to reverse engineer plugins from GitHub’s official plugin for VIM (or VSCode, other editors). And that won’t bring you any new feature but potential more issues in the future.
I can image one would be really a LSP hater, then he/she can begin his reverse engineer journey here: https://github.com/github/copilot.vim/tree/release/copilot/dist