Curt's point about the reality of low current flow most of the time is important. Usually the load (and voltage drop) would be much less than what you see at 150A. But his other point is critical. When things like the heat pump kick in, the short duration starting current will be much more than the full running current; even if you sized for 3% VD at 200A, the lights would still flicker every time a large motor kicks on.
What about the following approach:
From the pole to the house, run two sets of 2/0 conductors. Run the first set of conductors to a 150A panel, and place all of the 240V loads on it (heaters, heat pumps, range, etc). Run the second set of conductors to a 50A panel, and place all of the lighting and general purpose receptacles on this feeder. Make sure that all of the heavy loads are rated for operation on 208V as well as 240V.
This doesn't get rid of the losses in the wire; it just makes them less noticeable; the lights won't flicker when the heat pump kicks in, and the flicker in power to the hot water heater just won't matter. Presumably you could reduce the size of the neutral on the 'power' feeder...a pair of 2/0 conductors has roughly the same cross section as a single 250 kcmil conductor, so this essentially cuts your copper requirements in half.
The major code issue is that you are now running _two_ feeders to a detached structure. I think that you could get away with this as 'different characteristics' for the two feeders, and if both panels are located in the same place in the house, then the general concept of a single location for the main disconnect is met.
-Jon
