Not sure the 767s could cover the range about which you're talking; looks like it'd be close - range chart
here for LAX, prolly more doable from SFO. I
hope they don't, as we don't wanna give anyone any bright ideas...
Personally, I'd rather have a larger plane for long trips, much more comfy and more room to stroll. I wish UA had A380s on the long hauls...
Btw, BA tried the smaller plane/higher frequency strategy about a decade ago...didn't work. Nor did the different colored tails, but that's for another thread...