Hmmm Der Alte must feel pretty safe to go surfaced without four lookouts and a WO on the bridge.

Sub seen, sub sighted, sub sunk!!
Nitpicking a little: A REKO 52 is a DDR design. You might want to look up some of Killerkrabbe's little diesel tractors for pier work. To make it perfect a couple of V36 diesels and some French or Belgian steamers.
The 78 is not so far off the mark, since France claimed quite a few of those as compensation following WWI, but that would be for passenger service.
I believe there is a BR 58 on DLS somewhere, which would blend in just fine as well.
All that aside, just another great example of the versatility of this game.