You can convert to 260 with only a barrel change.
Depending upon your distance for shooting, you can go to 22" and loose some weight with very little if any performance lost.
For me, with either the 260 or 308 you will not need a brake.
You need to maintain some barrel thickness in the barrel under the handguard, but beyond that you can make the barrel fairly light.
Barrel twist for 260 should be 1x9 tot shoot the 140 grain bullets.
Barrel maker of choice for me is Krieger.
Switch barrel is pratical, but the bullet performance from the ones you mentioned are close enough to each other, I would just do the 260 or 308 and leave it alone.
You can get lighter stock and forend.
Thanks for the reply!