[RPG] How to the reach of natural attacks be increased

An Unarmed Strike is (kind of)¹ a natural weapon.

Not all natural weapons are Unarmed Strikes.

Natural weapon is a category of weapon, which includes Bites, Claws, Slams, Stings, Tail Slaps, and yes, Unarmed Strikes (sort of).¹ Improved Unarmed Strike improves only Unarmed Strikes, not the rest. Improved Natural Attack can improve any one natural weapon, except not Unarmed Strikes because Paizo hates Monks even more than Wizards did.

Note that Feral Combat Training changes this somewhat, however. Improved Unarmed Strike itself still doesn’t apply to natural weapon other than Unarmed Strikes, but anything that has Improved Unarmed Strike as a prerequisite does apply to the chosen natural weapons when you have Feral Combat Training, even if usually they only apply to Unarmed Strikes.

Ultimately, you’re burning two feats to absolutely no effect other than possibly making other feats work. If you found some really good feats that improve Unarmed Strikes, it might be worth it, but I doubt it. That’s a ton of feats. And honestly, I think a good DM should just let most Unarmed Strike-improving feats work for other natural weapons; this is not exactly a high-power strategy here. A two-feat tax is wholly unnecessary.

¹ I say “kind of” because Unarmed Strikes are really weird. They mostly follow the rules for manufactured weapons, not natural weapons (e.g. you get iteratives, you don’t get multiple Unarmed Strikes, etc.), but most spells and feats treat Unarmed Strikes as natural weapons. And on top of that, Paizo put a further restriction on Improved Natural Attack to prevent it from working with Unarmed Strikes. So Unarmed Strikes are very much a weird hybrid case. In any event, Claw attacks are not Unarmed Strike attacks.

One highly effective method of increasing reach in Pathfinder, not yet mentioned, is the Cleric Subdomain Plant(Growth). This option is different from, and superior to, many other methods of increasing reach in Pathfinder. This domain option provides more than just Swift Action Enlarge Person. It also provides the character with tactically valuable on-demand extra 5' steps.

Enlarge (Su): As a swift action you can enlarge yourself for 1 round, as if you were the target of the enlarge person spell. You can use this ability a number of times per day equal to 3 + your Wisdom modifier.

Replacement Domain Spells: 1st— enlarge person

Using the enlarge ability also provides the user with free virtual 5' steps!

I've played a Plant(Growth) Cleric in Pathfinder through 10 levels and can testify that it is extremely effective. In terms of reach, large size stacks with longarm. A Large biped wielding a reach weapon and buffed with longarm will have 25' reach and a ridiculous 60' diameter threat circle. The enlarge ability allows one to walk around normal-size yet swiftly become large if combat occurs.

The best part is the free virtual 5' step that comes from frequent starting and stopping of enlarge person. This is a tactical move that will make you smile every time you use it.

Getting Large: Your unbuffed longspear-armed PC can threaten 30' away with just a 5' step. Take a 5' step toward the foe, then swift Action enlarge person and choose to grow toward the foe. You now threaten the foe 20' away and still have your normal actions. It's as if you got an extra 5' step.

Getting Medium: Foes will quite reasonably feel threatened by the spear-wielding giant and may try to run in close en masse. Say foes survive your Attacks of Opportunity and move adjacent to you. When your turn comes around the first thing that happens is that enlarge person ends. Choose to shrink away from your attackers. They are no longer adjacent. It's as if you got an extra 5' step.

You can even 5' step away and swift enlarge person again, choosing to grow away, which leaves large you threatening foes who are now 15' away. You may full attack or safely cast a spell, yet foes will draw more AoOs if they want to close with you again. This works exceptionally well for area denial builds using a reach weapon. You can prevent foes from landing a Full Attack, yet you can always Full Attack.