The use of gradients breaks the Shipbucket style, which is designed to be plain and simple to reproduce using just MSPaint. Limit your tumblehome depiction to 2 to 3 colors maximum and I think it will fit within the style guidelines given the extraordinary requirement.
Hello there
OK, a maximum of three colours it is then. It will look like that (the old shading template above, a new one reduced to three colours below):
Please inform me if that's OK and I shall change the drawings.
PS having said that, the old shading style actually was hand-rendered with MS Paint. Took 15 minutes, was the same one on every ship (scaled to two different widths). MS Paint is the only program I use, for anything more complicated I am too... don't know. Old, or dumb, or not nerdy enough. But hey, rules are rules.
Greetings
Garlicdesign