A while ago I made a dodgy photoshop
Would love a 3 Wheeler looking like this, but would have to be painted and not a decal so it would look even better after a few years weathering.
The intention of using the Decals is that they could be changed if you became bored with them, or wished to sell the M3W. - mind you I agree about weathered look.
As for WWII Decals, I believe that others share your thoughts.