Yes!
We have several trucks setup with tanks in box that are plumbed into the vent line with a "T" in the vent line. You can either use a ball valve and manually open and close or add a solinoid valve to control flow on the fly from a switch inside cab.
We do NOT have return lines, do NOT have inline filters, and do NOT have punps. We do build the tanks to suck directly off the bottom of the axillary tank.
I have transferred about 6,000 gallons trough the axillary tank in my truck alone.
It is simple, it works!
jjw