Search the file in your main SH4 directory:
Your SH4 folder\Data\Roster\American\Submarine\Your class of boat
Example: Gato class---->SSGato.cfg
In this file, delete all the name units you don't like. In my cfg file, I always want the Silversides, so the file is:
[UnitClass]
ClassName=SSGato
UnitType=200
AppearanceDate=19411101
DisappearanceDate=19721015
DisplayName=US Gato
[Texture 1]
TextureName=data/Submarine/NSS_Gato/NSS_Gato_T01.tga
LightmapTextureName=data/Submarine/NSS_Gato/NSS_Gato_O01.tga
StartDate=19411231
EndDate=19421231
Frequency=1
[Texture 2]
TextureName=data/Submarine/NSS_Gato/NSS_Gato_T02.tga
LightmapTextureName=data/Submarine/NSS_Gato/NSS_Gato_O01.tga
StartDate=19430101
EndDate=19601231
Frequency=1
[Unit 1]
Name=USS Silversides (SS-236)
DOC=19411101
DOD=19460216
;************ The End ************
You can delete all the subs you donīt like and leave all you like. Do you want to send Mush Morton to a desktop work? Leave only the Wahoo. Do you like to command the Barb and donīt leave that badass Flucky Fluckey take your sub? Leave only the Barb. Also you can replace a sub with your own name, for example SS-777 USS Onkel Neal.
It works restarting campaign.
Good luck!
Fitzcarraldo