What a larger Rothesay-class frigate could carry

What might a larger Type 12M Rothesay-class frigate carry in place of, or alongside, its torpedo tubes?

Extra displacement could support more Sea Cat, retained torpedoes, stronger anti-submarine equipment, or improved aviation space.

Historical Rothesay-class refits paired Sea Cat with Limbo, while some ships never received their intended torpedoes. A larger hull would not dictate one fixed armament, but it would create room to retain torpedoes, add another Sea Cat launcher, strengthen anti-submarine equipment, or improve hangar capacity.