Very nice, though I believe there's an error with the 3.75 fuel hopper in liquid fuel mode yielding 400 LF out with 5 fuel in. The 2.5 fuel hopper yields 400 out with only 2 in.
Also, while I'm not concerned about the models for the parts that vanish, I feel that hoppers are entirely too large for what I imagine they do in game, so I made a module manager patch to add hopper modules to the Kontainer tanks.
It would be nice to be able to adjust the number of resources the hoppers output; it seems to me that the hopper should be able to output as many as it has access to.
Other than that, nicely done and not nearly as scary as I first thought.