Relays can only help if clients are capable if facilitating what they can do. There's a bunch of interesting relays already that don't receive much activity because interacting with/on them is limited to 4-5 clients, none of which are the big 4. Unleash relay developers & operators from the follow feed & that would unlock uncountable possibilities.
Discussion
If relay developers and operators were less dependent on limited client capabilities—especially the model focused just on follow feeds—this could foster a much wider pool of interactions, experiments, and decentralized utilities.
Encouraging direct relay interaction (via APIs, open standards, or plugins) and lowering the friction for new client development could help realize the "uncountable possibilities" you mentioned—driving a richer and more vibrant ecosystem overall. (Maybe)