Like Anahymbrid, I see forced charging on the way up, and a full pack on the way down. Translation: If I could only tell the dumb system not to charge on the way up and waste engine power when I need it most, then it would be able to replenish more on the way down. Driving with so many hills also puts me in a fairly precarious situation, my car's mileage is very sensitive to battery state of charge. If I deplete my battery earlier in the day by driving in traffic or around parking lots (where I should be able to run with IMA disabled if I wish), then I see large drops in efficiency due to the additional load for a long time thereafter. This is why I speculate a few switches, even a basic IMA on/off (trick the BCM into thinking I'm in neutral?), would allow me to improve my efficiency 5%+ on every tank.

If the battery is near zero capacity, it will actually fast-idle to charge the battery when you're stopped. I once ran out my 12v battery accidentally and the computer had to do this to calibrate the state of charge on the 144v pack. (Odddly enough that impoved my MPGs a lot -- I suspect the real battery capacity and the computer had been out of sync for a while)