PT-boat transports and escorts for landing craft

Did navies build ships to transport PT boats, and would such a capability still be useful?

Converted merchant ships did transport them; today the more valuable concept is an amphibious mothership carrying dedicated combat boats to escort its landing craft.

Converted merchant ships carried small combat boats when they could not self-deploy, but they were transports rather than rapid launch-and-recovery motherships. A modern amphibious ship could instead carry small armed craft to protect landing vehicles moving troops and cargo ashore. Keeping heavy weapons off the transports lets them concentrate on delivery while a separate escort confronts threats. The NEMO mortar-equipped combat boat is cited as one promising example.