"total conversion" is one of the most coveted and difficult modding projects one could undertake: Making a new, bespoke campaign using the mod tools of a pre-existing game, with the end result unable to be monetized due to copyright (unless you're working with the beautifully open source Doom engine). At a certain point, you'd probably be better off just making your own indie game, and that only makes these Moby Dickian efforts all the more enticing...
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