Since we're just dreaming here... .
I'd use the Montana action and build it in 300 Lapua.
I'd put a sendero tapered barrel but carry it on out to 30" to finish at around .750.
It'd be a 3 groove progressive twist ending in a 1:10 for maximum velocity and accuracy.
I'd finish it with one of Kirby's muzzle brakes
, or another Snowy Mountain Rifle's brake since I have several of them already.
It would of course all be stainless and cerakoted probably in tan/sand.
I'd build it on a Precision Rifle stocks hunting stock or maybe an A3 Hunter McMillan with the lightest kevlar/epoxy fill they have.
Shooting the heaviest 30 cal VLD/hunting bullets out there it should make for a 1,500yds monster killer.
There are too many things that can change down range for me to think shooting game beyond that range is responsible due to the flight time. An animal can move a long way, or another can move into the line of flight unintended, very easily when flight time exceeds 1 second.