Tower Shield Specialist. First off, let's explain some things. Valerie is not a good TSS. She's a great companion, but sucks at being a TSS. She is better off as a base fighter. A TSS requires decent stats to be fully effective, which Valerie lacks, due to her unique stat spread. The main problem is her INT and DEX. You need 14 DEX minimum to squeeze additional AC from heavy armor. In the early game you need all the AC you can get for your tank. Not starting with 14 DEX hurts. Another thing is her INT. You need at least 13 INT to qualify for combat expertise. This feat is huge, it opens up a lot of options for martial users. It also gives AC. Which you kind of want for a front tank.
With that out the way, lets talk about the class and the kind of build you will want on it. In my opinion, TSS is a valid choice for an early game tank. It doesn't need much to be decent except for basic gear and feats. It also continues being a decent tank in the higher levels, of course it gets outclassed by your sword saints, monks, and mirror image users. Anyways, what do I mean when I say it is a valid choice for an early game tank. Now do be noted, since I am using the DLC dungeon. I will have access to heavy armor at level one. In the main game, you don't get access to heavy armor until later, specifically after you leave the prologue area. But, that's okay. The point is to portray just how effective the TSS can be in the early levels with decent equipment.
Here is how much AC the TSS can achieve at level one:
Twenty five AC is quite good. It coupled with fighting defensively = nice AC. But that was with heavy armor. Here's what it looks like with medium armor(Which is what you start with in the prologue):
Again, twenty three AC is not bad at this level. Especially for the early game. With the feats Dodge, Shield Focus, Heavy Armor focus, and Fighting Defensively. The TSS is able to reach decent AC.
Due to the unique nature of the class however. This isn't something I'd recommend for a main character. Unless of course, this is a class you want to play. In which case, go for it! In any case I feel this class is better suited for a mercenary. As this class's main function is to primarily front line. Alright. Let's talk about the kind of feats and stats that I think you'd want to run with on your TSS.
Race: You can go Human for extra feat. Aasimar for the wings. Dwarf for steel soul. Halfling for cautious fighter. Or tiefiling for the Shackleborn heritage. For this demonstration I will be using a human.
Class: There is a lot of ways to go about this. Here the different class combos you can do. Pure TSS is also perfectly fine if you don't want to multiclass. Lets first talk about vivi. Four levels of vivi is nice because it gives us the ability to pick preserve organs. This gives you a 25% chance to negate a critical hit or sneak attack. Pretty good for someone that is going to be face tanking. If you go four levels you can pick the feat twice, further increasing the bonus to 50%. You can also dip six levels of vivi to pick the feat three times. Thus increasing the bonus to 75%. Really good. Stalwart Defender is another good choice. You can go up to five or even ten levels. This gives you access to AC stance, bonuses to AC, DR, and uncanny dodge. All good stuff. Another is a level one dip into monk. This allows easier access to the crane style feat, also good. There are other class combos you can do, but the ones listed are the main ones that you need to know if you want to increase your tanks potency.
Stats: The main important thing is getting DEX to 14 and INT to 13. A high CON is necessary because you don't want your main front liner to die from a couple hits. You also need a decent WIS as well. An example of a stat spread will look something like this:
STR 14
DEX 14
CON 16
INT 13
WIS 12
CHA 8
Feats: Here are the feats I recommend running:
Armor Focus (Heavy Armor)
Dodge (A prerequisite for stalwart defender)
Shield Focus
Toughness (More health. Also needed to become a stalwart defender)
Improved Initiative (Initiative is always nice on a martial character as it minimizes how long it takes for them to act)
Combat Expertise (This feat is huge. In addition to granting AC bonuses. It also opens us up to use dirty trick. Dirty trick is amazing because it targets CMD. It also gives us something to do besides face tanking.)
Outflank
Combat Reflexes (This in conjnction with Outflank increases the amount of AoOs you can dish out)
Iron Will (Will saves are very important in Pathfinder: Kingmaker. There are a lot nasty spells that attack will)
Improved Iron Will
Shake it off
Missile Shield
Blind Fight
Weapon Focus (Long Sword - This is due to the fact that there long swords that grant bonuses to AC.)
Improved Blind Fight
Greater Blind Fight
Greater Dirty Trick
Crane Style (Super nice as it grants an additional point of AC when used with fighting defensively. Need three ranks of mobility to benefit the most from it though.)
Greater Shield Focus
Combat Mobility (It's not vital. But its nice as it gives you an additional AC when moving towards or out of a threatened area. Makes breaking from engagements to cover the flank easier.)
Sunder Armor (A good alternative to dirty trick. Used to chip away AC from an enemy.)
Greater sunder armor
Lighting Reflexes (Having decent reflex saves is welcomed)
Improved Lighting Reflexes
Improved Critical (For AoO procing)
Greater Weapon Focus
Crane Wing (This feat is bugged and works with shield users.)
Okay, here's an example build that can reach decent AC even on the high levels:
Race: Human
Class: 20 TSS
Stats:
STR 16
DEX 14
CON 16
INT 13
WIS 11
CHA 7
Level 1 - Tower Shield Specialist - Feats: Armor Focus(Heavy Armor), Dodge, Shield Focus - Skills: Mobility, Perception, Knowledge(World), Athletics.
Level 2 - Tower Shield Specialist - Feats: Missile Shield - Skills: Mobility, Perception, Athletics.
Level 3 - Tower Shield Specialist - Feats: Improved Unarmed Strike - Skills: Mobility, Perception, Knowledge(World), Athletics.
Level 4 + 1 WIS - Tower Shield Specialist - Feats: Crane Style - Skills: Mobility, Perception, Athletics.
Level 5 - Tower Shield Specialist - Feats: Outflank - Skills: Mobility, Perception, Knowledge(World), Athletics.
Level 6 - Tower Shield Specialist - Feats: Combat Expertise - Skills: Mobility, Perception, Athletics.
Level 7 - Tower Shield Specialist - Feats: Toughness - Skills: Mobility, Perception, Knowledge(World), Athletics.
Level 8 + 1 STR - Tower Shield Specialist - Feats: Greater Shield Focus - Skills: Mobility, Perception, Athletics.
Level 9 - Tower Shield Specialist - Feats: Dirty Trick - Skills: Mobility, Perception, Knowledge(World), Athletics.
Level 10 - Tower Shield Specialist - Feats: Greater Dirty Trick - Skills: Mobility, Perception, Athletics.
Level 11 - Tower Shield Specialist - Feats: Crane Wing - Skills: Mobility, Perception, Athletics.
Level 12 + 1 STR - Tower Shield Specialist - Feats: Power Attack - Skills: Mobility, Perception, Athletics.
Level 13 - Tower Shield Specialist - Feats: Combat Reflexes - Skills: Mobility, Perception, Knowledge(World), Athletics.
Level 14 - Tower Shield Specialist - Feats: Weapon Focus (Long Sword) - Skills: Mobility, Perception, Knowledge(World), Athletics.
Level 15 - Tower Shield Specialist - Feats: Shake it Off - Skills: Skills: Mobility, Perception, Athletics.
Level 16 + 1 STR - Tower Shield Specialist - Feats: Improved Critical (Long Sword) - Skills: Mobility, Perception, Athletics.
Level 17 - Tower Shield Specialist - Feats: Iron Will - Skills: Mobility, Perception, Athletics.
Level 18 - Tower Shield Specialist - Feats: Greater Weapon Focus (Long Sword) - Skills: Mobility, Perception, Athletics.
Level 19 - Tower Shield Specialist - Feats: Improved Iron Will - Skills: Mobility, Perception, Athletics.
Level 20 + 1 STR - Tower Shield Specialist - Feats: Blind Fight - Skills: Mobility, Perception, Athletics.
Here's how much AC it can reach in the high levels:
As you can see. TSS can reach respectable levels of AC in both the early game and late game. The problem is that the class is outclassed by Sword Saints, Monks, and Mirror Image users. But if you're looking for an alternative to those builds, then look no further. TSS is more than capable of filling the role.