Bake, if you really want the sling hold option on a big bore, there is no law that says you can't have a custom stock made that positions the sling swivel far enough out that no contact with the support hand is possible. It would not be traditional, and probably the sling would see little or no use, but so what, if you wanted such a setup it could be had.

The front sling swivel on my Sako .375 H&H Mag is mounted on the stock. I've never had a serious problem with the swivel biting me as the recoil level of this rifle is not so violent. I have used the sling for support several times in the field over the years, so it is not a worthless appendage.

I can see where a one-gun hunter in Africa who is used to shooting with a sling might want such an option even on a fairly heavy gun, say such as a .416 Rigby/or/Remington as such a rifle is flat enough shooting for all types of game and heavy enough for the Big 5.

I think many people have their highest interest in traditional gun designs. For myself, I always enjoy seeing highly personalized guns and find customized touches that address the nuances of personal taste, physique, build, habits and comfort to be fascinating.