Why grey-zone warfare changes the OPV armament question

Does the case for better-armed offshore patrol vessels mean navies should recreate a sloop-like intermediate combatant?

Not necessarily; the key is giving patrol ships proportionate self-defence for prolonged and grey-zone conflicts, not changing their label or making them full frigates.

Better-armed patrol vessels can remain OPVs within the existing force structure. Their protection should reflect the threats they may meet. Cold War planning often assumed a major conflict would become nuclear quickly, reducing the expected wartime role of patrol ships. A prolonged conventional or grey-zone confrontation instead leaves them exposed to commercial drones and other weapons that a state can quietly supply to motivated proxies. Deniability requires enough alignment for money and equipment to reach an attacker, even when the sponsor and actor do not share every objective. Limited defensive weapons can therefore be justified without turning an OPV into a strike combatant.