I agree with the Kettenkrad Repair, but the Cloak i don't find very useful. Sure, it can come in handy in the ways you said, but the reduced speed means it will likely get spotted anyway, either by not being able to escape advancing enemies, or having to de-cloak to get away.
And Schwimmwagen Mines can be real handy. It's a fast little unit, so it can get in there and place Mines much quicker than infantry. Similar to the Greyhound, but obviously not as effective.
