This is obviously an area where the shifting models of software in general
and emacs in particular have changed over time (by a rough count, non-Gnu
Elpa is roughly the 8th-10th "emacs lisp archive" I've personally used),
and there are clear experiments in play right now. As a practical matter,
how would people feel about a sort of autoload variation, included in emacs
(30) core, that points users at relevant packages in [non-]GNU Elpa, which
would be overridden by code included in an actual package? The idea is to
combine a thin pointer with a potential indirection point that allow users
(who had not already chosen) to choose between alternatives such as
clojure-mode and clojure-ts-mode.

Hope that helps,
~Chad