I'd hardly call the .270win and .280rem 'handicapped' with heavier bullets.
What's wrong with the .277 shooting a 180 grainer at 2500-2600fps, or the 280rem shooting a 180 at 2600-2700fps. The 06 is slightly more efficient and pushes a 180 to around 2700-2800fps, but it's going to lose it's velocity faster assuming all the bullets have a similar VLD shape, and have similar core material
What's wrong with a .270 Winchester shooting a 180 grain bullet, is that your velocity figures are highly optimistic and unachievable in the average rifle. In reality, the velocities of a 180 gr projectile are more like 2,300-2,450 fps (even 2,500 fps can be difficult to achieve).
Even with the extra case capacity and higher pressures allowed in .280 AI (versus standard .280), you're still lucky to be able to hit 2,600 fps with a 175 gr bullet.
And, arguing about ballistic coefficients doesn't do much good without some actual comparisons.
How about a "best case" .270 load against a "worst case" .30-06 load with bullets of nearly identical BCs :
.270 Win Wooleigh 180 gr (0.512 BC) @ 2,500 fps - At 1000 yards: 1193 fps / 485" drop / 98" drift / 569 lb-ft energy
30-06 Sierra GK BT 180 gr (0.507 BC) @ 2,700 fps - At 1000 yards: 1282 fps / 412" drop / 89" drift / 657 lb-ft energy
The .30 caliber projectile has a huge advantage with the increased muzzle velocity. It is farther from destabilizing (subsonic transition), drops 73 inches less than the .277" projectile, drifts 9" less, and retains 15% more energy.
Even if you turn to a "best case" .280 AI vs "best case" .30-06 for the same comparisons, the results still favor the .30-06 for nearly anything in the 170-195 gr weight range.
If you REALLY want to build a .270 or .280, go for it. But don't worry about things like down-range efficiency, unless you actually run comparisons to verify your assumptions.