One more use I just came across: placing anti-ship mines.
For example: during several nights in late April 1943, RAAF 11 Squadron used their PBYs to lay mines in both Silver Sound and Ysabel Passage between New Ireland and New Hannover (near Kavieng) to counter Japanese supply ships headed for Rabaul. This was likely the earliest use by the RAAF of the PBY for mine-laying.*
In-game, mines might possibly delay CV respawns, actively sink ships that hit mines, delay supply barge respawns, etc.
* see "Australia in the War of 1939-1945: Air War against Japan 1943-1945" by George Odgers