It wasn't going to be.
Everything you've tried you had to have bought ammo for at some point yes? Every box of shells shows a different grain weight that or bullet construction designed with specific animals in mind. Even within each caliber there's generally a very wide selection of bullet weights tailored to specific animals. Let's take .30-06 as an example here.
It uses a .308 diameter bullet, varying generally between 110 and 220 grains outside of custom made bullet moulds. All those bullets will follow a construction principle with a general type of animal in mind. Like the 220 grain will generally be a soft point design with a round nose, this design allows it to punch extremely deep or shatter thick bones and hold together enough to pass through the vitals of big animals like moose and brown bear.
Now, the same caliber has access to 150 grain polymer tips. Poly tipped rounds are in essence hollow points with a nose cone so they fly better. These are generally meant to reach out longer distances, generally for animals like pronghorn antelope, deer, and wild sheep. The poly tip makes the bullet fly accurately and once it hits the target the tip forces rapid expansion. A sheep or deer generally has a 17 inch chest cavity so if the bullet over penetrates it could either be a wound or an extremely slow death and difficult or impossible tracking.
Covering every animal between whitetail (4) and moose (8) with a single bullet can be done but generally it's not ethical or practical. So I don't think it's stupid at all to have classes ranges for each rifle. That 220 grain for brown bear (7) and moose (8).
And a 150gr for whitetail (4) and rusa deer(6).
This is the easiest way I can think of to make a decent Overhaul that won't kill development time needlessly