I would recommend a 24" #5 Lilja stainless fluted with Dans heavy 50 BMG style flutes.
McMillan does offer a thumbhole, it is the Lazzeroni model which can be inletted for a Rem 700 easily, not a problem.
I did not realize H-S offered a thumbhole in a sporter stock. If its their tactical thumbhole this stock is not light. In fact the Boyds Laminate thumbhole sporter is lighter then this stock and once it is pillar bedded and the barrel floated extremely stable as well.
That along with a fully accurized Rem 700 receiver and the addition of an aftermarket match grade recoil lug, I use Holland or Badger Ord recoil lugs, you would have a very stable, light weight rifle.
The Rem factory triggers can generally be tuned down to 2.5 to 2 3/4 lbs with consistancy and total safety. If you want lighter then that which I do not recommend on a light weight big game rifle, I would go with an aftermarket trigger.
I would recommend a Holland QD muzzle brake as well as these are the most efficent brakes I have used that are designed for the needs of a big game hunter.
If your interested in my prices for such work drop me an e-mail at firstname.lastname@example.org
Generally my customers tell me what they want in the rifle and I order all the componants so they do not have to deal with that aspect of the adventure as it can be a bit intimidating for someone not used to ordering componants.