You can actually buy weapons others have made, but you have to pay with ingame gold, so it'll cost ya.
Good/interesting thing is that there is no real end-game content for as far as I can see. So if the goal is to just derp around in ridiculous vehicles, who cares if you're low level?
Just looking real quick, it looks like there were some attempts to turbocharge the DB 605/603/601 engines, along with the Jumo 222, but they don't appear to have ever gone anywhere. I'm guessing Germany would have had severe difficulty producing turbocharged engines due to a lack of materials (similar to the issues their jet engines had).