Looking at the history of the Monsun Gruppe or Monsoon Group on Wikipedia.
This history might be an option to add German/Italian Squads to the Japanese and Japanese Squads to the Germans. These squads could be made up of ex-submariners of various classes already in the game (Medic, Assaulter, Radio Op, and Engineer). These would be great premium squads.
The German and Italian help the Japanese with submarines and the Japanese help the Vichy French against the British in Madagascar.
Nonsense
They mostly did patrol job.
Average submarine crew is not rambo or arnold schwarzenneger. You seem to have no idea about naval warfare and confuse marines with u bot crews whos main basic job is running and fixing machinery.
Italians faired the worst; all italian subs were destroyed or captured even before they managed to go beyond oman sea.
Kriegsmarine had marine corps but they were ill equipped, less experienced than us marines or royal marines. Their parcitipation in ww2 was very limited to insignificance level and NEVER left europe.
Its suggestions for a computer game not a history book. The game is already inaccurate. It was a very creative suggestion to copy paste some squads.