Rifleman10x
I don't think there will be a big demand. The people who love and shoot the .35 Remington seem to love the classic, old fashioned nature of the cartridge, including the big round nose 200 grain soft point. These rounds are very effective for their intended purpose and will stop any deer or black bear at 150 yards or under, which is all that the carbines for which they are chambered are intended..
You will occasionally find a person who uses his .35 Remington for Elk etc., but the vast majority of people who are going to hunt an Elk will set aside their lever .35, and lift that scoped 30-06 or .300 mag from the gun cabinet.
If your company wants to go in this direction, then I respectfully suggest that you offer the Starfire round in the .358 Winchester instead. This round has a cult following, and most people who love levers are going to buy one in this caliber sooner or later. In the past year or two, there has been lots of interest shown in this round on this boad. The production of the Marlin Guide Gun in big bore calibers has generated a yearning for new rifles in this caliber.
Sell good ammo in .358 Winchester, and people will buy it!
Best Regards,
Paul Amos