Maybe this is what Australia is after?
Block V Virginia class VPM nuclear powered attack submarines
The VPM adds four large payload tubes in a new hull section, increasing the submarines’ Tomahawk strike capacity from 12 to 40 missiles per boat. The VPM will also enable robot vessels to be carried. The VPM will also enable special operations forces and allow the U.S.A. Navy to carry additional weapons. The VPM, Block V subs will also have “British” acoustic design changes. Virgina class subs displace 7,800 tons, with a hull length of 377 feet. With VPM the subs will displace 10,200 tons and will be 460 feet long.
Some upgrade.