Why enlarging the U class duplicates the T class

How could a U-class boat be made more survivable and enlarged for service in the Pacific?

The response is to use a T-class boat, which was already designed for Far Eastern and Pacific service.

A question about greater crew survivability and the range to reach Australia is interpreted as referring to the U class. The proposed answer is to send a T-class boat. British submarine classes already divided the work according to their operating environments. Enlarging a small coastal design for Pacific distances would overlap the role for which the T class existed.