That's a fair point Erik. Sea Cat is intended to replace the 40mm Bofors, in its earlier MRS-3 guided form its no anti-missile missile. It does well at close-in AA work but its subsonic. Orange Nell is not an area-defence weapon, that role is for Sea Slug, Orange Nell is designed as an anti-missile system. In effect the Type 80 is a goalie. Now I could have made her a double-ender and put a second Nell aft instead of the flightdeck but that would have meant losing the Wasp and possibly Limbo. I wanted the Type 80 to have an ASW escort role too, she meant to be a Type 12 with the 4.5in replaced by a missile system as the Admiralty intended doing. She is a goalie protecting the carrier with the County or Admiral (both of which also have Nell) further out for area defence. I figure the vertical 40-round magazine would be pretty bulky and would require a lot of internal space.
And because Sea Cat is light it makes sense to fit it to make a double-ender ship without the loss of capablity and gorwth in hull size and weight two Nells would require. Like everything, you have to compromise somewhere.
I don't mean to suggest a second Orange Nell - rather, nothing at all. Or perhaps keep the 40mm right through the Sea Cat era. Even this scenario surely involves economies, and including a second system that effectively duplicates a subset of the first, while adding a (granted, small) additional chain of spare parts and trained crews... it just doesn't make sense to me. Certainly one never saw Sea Sparrow appear on Tartar ships. It'd be nice if money grew on trees, but I'd rather spend that cash getting more Orange Nell into the fleet (even if on different ships).