Is that a B-vent for some sort of heating appliance coming out of the wall? It seems much too close to the tank and your future fueling area.
I know it"s a Diesel tank and Diesel is not as volatile as gasoline, but I really think the tank should be farther from your building, especially in light of the flammable wood wall right next to it. I"d also get it away from the door if I could do so without too badly compromising convenience in fueling
I would probably place any disconnect means away from the meter/fueling area. You can still meet the "in sight of" criteria for future service needs, but not risk an arcing disconnect switch near where fuel is likely to be spilled.
(This assumes the pump has its own shut-off switch should you need to kill the flow of fuel quickly).
The electrical code has all sorts of special provisions for "hazardous locations". I"m not sure whether a Diesel fuel pump constitutes one of these "hazards", but just from my own experience the proposed installation strikes me as "not as safe as it could be".