Why HMS Unicorn still belongs in a larger treaty-carrier fleet

Would a Royal Navy with more 27,000-ton carriers still build HMS Unicorn?

Yes; Unicorn's maintenance, supply, and small-yard construction roles remained distinct from those of a full-sized fleet carrier.

Doubling treaty carrier tonnage would not eliminate the need for HMS Unicorn because she was designed to support aircraft and carriers where shore infrastructure was scarce. Her size followed auxiliary limits and allowed construction in yards unable to build a full fleet carrier. The same compact hull logic later made Unicorn a natural reference point for wartime light fleet carriers. Making her larger for a few more aircraft would undermine the distributed construction and support role that justified the ship.