So that's the mysterious Keltos live and in person...
I'd give the top priority to the second model you posted, the Seehund.
The Biber was the most lethal weapon of WW2. To its drivers, that is...
It could dive, but could not keep depth, so dives in the Biber were either very short or permanent. Usual modus operandi was to dive only to avoid obstacles like antisubmarine nets and remain on the surface the rest of the time.
However, the main problem of the Biber was its engine: An Opel Blitz truck engine. Not a diesel, but a gasoline engine, which gave off carbon monoxide that slowly poisoned the driver. I suppose most Biebers were either lost to carbon monoxide poisoning or to fatigued drivers getting lost.
Bibers sunk a single confirmed enemy vessel, the 4000 ton "Alan-a-Dale".
The Seehund, in contrary, was a real U-Boat that could dive almost as fast as the IXD2 in the current ATO expansions:rotfl:
It had a working snorkel, a good range and good underwater performance. Also it was supposedly immune to depth charging because it was so small it was rather tossed around by the explosions than demolished.
Problem was, the 2 man crew had to endure missions for days without getting any sleep or toilet, with no navigational aids constant danger. I suppose most of them were high on Pervitin (basically the Bayer version of today's Meth) or at least on "Schoka-Kola" caffeinated Chocolate.
Seehunde were quite successful, with about 100.000 tons of shipping sunk.
So if you make one of them drivable, use the Seehund.
Of course the Biber would have the distinct advantage of having to create only the conning tower view, while the Seehund has a distinct interior.
But AFAIK the only real damage a Biber ever did was:
- one accidentally shot a torpedo into a whole Flottilla of Bibers, setting off a chain reaction that destroyed over 30 Bibers and killed many drivers
- They (kind of) successfully torpedoed the Bridge of Nimwegen
But both are rather slow and I don't know wether SH4 would simulate shallow water ASW and operations, especially since the operation area is one usually left blank in SH3-4 campaigns, the dutch coast and the Channel.
Also, fire control was rudementary on both. Basically, the driver aimed by "Seaman's Eye" and let fly. The problem was that the torpedoes were modified to be lighter but slower, and were only around 20 knots, so anything but a stationary target is a matter of luck.
Another mission would be supply missions to cut off german garrisons on the Channel coast.
A good novel on that topic is "Der nasse Tod" (wet death) by Enrico Döring.
If not for a cheesy romance subplot, I would even rate it as the best german language sub novel in a long time.
Same author now wrote a nonfiction book "die Biberfahrer" (the Biber drivers) about the subject.