I just had a thought, Uh-oh.

If I put a filter in the fuel jug on the line..... use a t-connector after the filter (on the out, side) and install a check valve.... all inside the jug. That way, when you fill the tank, it'll pull fuel through the filter. When you de-fuel it'll route through the check valve back into the jug (and not through the filter). Junk will collect in the jug and the filter, but everything else stays clean. I hope that makes sense. Now'd be a good time for some nice ascii drawing, but I'm not gonna try[:'(]