Simply put, there's no reason to have rifle and shotgun perk trees as separate categories. Many of the perks overlap and could be used interchangeably.
Recoil management, shotgun tree, is just as necessary for accurate rifle shots as any other perk.
Both eyes open, shotgun tree, would make a clearer sfht picture for the rifles as well as handguns using open sights.
Fast shouldering, shotgun tree, already applies to all weapons and increases ready speed
Zeroing, rifle tree, affects all weapons and can be the difference between missing and accurately taking a diamond.
Steady Hands, rifle tree, affects all the weapons makes the ADS for any weapon easier to accurately fire (Note* aim wobble is absolutely atrocious on console and we need at least 3 more levels of this or a fix to the motion sickness inducing scope wobble)
Focused shot, rifle tree, would be extremely useful for any weapon and much more useful in the early game than locked at the end of a skill tree.
Breath control, rifle tree, affects all the weapons equally and is arguably a core perk for any and all players, it should be integrated without the need to actively spend perk points.
Merging the skill trees would give players much more flexibility and control over their playstyle than the current system which would make gameplay more fun and fluid.
Increase the maximum hunter level to 100 with perk points awarded every three (3) levels and skill points awarded every five (5) levels between 60 and 100.
Pair this with an end-game perk system called the Mastery perks. For each class of weapon (Rifle, Handgun, Shotgun, and Archery) allow and extra perk selection that functions as the Mastery Point.
Mastery Points would further effect scope sway, accuracy, reload speed, and general performance. A hunter with ten points in Rifle Mastery would have extremely low scope sway, light recoil, +50% (base) extended effective range and 25% more penetration. (Pumping Iron, Archery perk)