eglot keeps a list of servers to spawn in eglot-server-programs but will very happily try to run without having a server program configured for the current major mode.
I would argue that we would very easily simply check for case in lsp! and handle it gracefully which would also allow us to simply have a “yes, I would very much like lsp enabled where possible”-flag and call lsp! for all modes.
Any issues with that approach? If not, I’ll drum up a PR.