The 6.5mm bullet has a great balance of high ballistic coefficients, bullet weight, and velocity, all out of a short action, low recoil gun. Bullet selection is excellent, as are the many chamberings for the caliber.
The 260 Remington is an excellent choice for overall ease of loading and shooting.
If its going to be a everything gun, I would start just as you had originally posted. Trued Rem short action, 1-8 or 1-8.5 barrel twist chambered in the original 260 Rem, finish the barrel at 24 inches and a HTG stock. If you plan on running the 130 grain and heavier bullets you are going to want at least a 24" barrel or you will lose a significant amount of velocity. The 120 grain and under bullets would be fine at 22"
I have a 260AI,an I absolutely love the caliber. Mine is built to be a long range light hunting rifle.
Remington Titanium action, Shilen 1-9 twist, 24" barrel carbon wrapped by Christensen Arms, Leupold vx7 with B&C Reticle and turnouts to 1000 yards, and a carbon stock. The whole package weighs in at 7.5 lbs. I shoot 139 Lapua Scenars at 2850Fps and Berger 130VLDs at 2900.
All that said my next gun that I'm in the process of building is a standard 260 Remington built off of a Surgeon action with a 25 inch barrel AICS stock and Leupold LR/T Glass. It will be more of a practice and shooting gun rather than a hunting rifle. I have found that on my 260 AI the amount of velocity gained is only about 50-100fps in my 24 inch barrel not a huge gain, but velocities vary from barrel to barrel.
Fire-forming the AI case is an added step for preparation before you have your final loads. My fire-forming loads are about 100fps slower and about 1.5 MOA different poi FWIW. But fire-forming isn't all that bad and shouldn't deter you from the benefits of the AI caliber if you want to mess with a wildcat cartridge.
Here is a pic of my hunting rifle.