We can build a lighter weight sporter, no problem at all. Thing to keep in mind is that these rounds produce a high degree of barrel stress when you drive a bullet of this weight and length to these velocities in a fast twist barrel.
As such, there is nothing wrong with a shorter length barrel. Even in a 27" pipe they work very well, of course there will be a big of velocity lose but if portability is more important then 75 to 100 fps at most, then why not.
One example is with my two 7mm AMs, one is a 9.5 lb lightweight with 27" #3 Lilja barrel, the other is a 15.5 lb semi heavy rifle with a 30" Rock barrel.
The 27" barrel will top out around 3200 fps with the 200 gr ULD RBBT, I load to 3150 just to be comfortable. The 30" barrel will do 3350 fps pretty easily but again I load a bit off max at just shy of 3300 fps.
I have never felt lacking with the shorter barreled rifle and used it to take 6 head of big game past 650 yards last year in 7 shots.
Barrel length is nice on an open country rifle, for a more general purpose rifle, there is nothing at all wrong with a 27-28" pipe with any of my conventional sized Allen Magnums.
Kirby Allen(50)