Would you allow those two to be used together?
The ruled do not forbid it.
Prerequisites: Base attack bonus +1, halfling.
Benefit: You can choose to take a –1 penalty to AC to gain a +2 bonus on melee damage rolls against creatures two or more size categories larger than you. When your base attack bonus reaches +4 and every four levels thereafter, the damage increases by 2. The bonus damage is multiplied in the case of a critical hit. You can only choose to use this feat when you declare that you are making an attack action or a full-attack action with a melee weapon. The effects last until your next turn.
The idea is to combine crane style and cautious fighter with defensive fighting to get decent AC for an unarmed build and add risky striker for a damage boost vs. large opponents.
Honestly this seems like an amazing idea and by RAW it works, this setup also has great synergy with one another.
I'm now thinking about my own Hafling build using this.
You can choose to fight defensively when attacking. If you do so, you take a –4 penalty on all attacks in a round to gain a +2 to AC until the start of your next turn.
Fighting Defensively as a Full-Round Action
You can choose to fight defensively when taking a full-attack action. If you do so, you take a –4 penalty on all attacks in a round to gain a +2 dodge bonus to AC until the start of your next turn.
Your unarmed fighting techniques blend poise with graceful defense.
Prerequisites: Dodge, Improved Unarmed Strike, base attack bonus +2 or monk level 1st.
Benefit: You take only a –2 penalty on attack rolls for fighting defensively. While using this style and fighting defensively or using the total defense action, you gain an additional +1 dodge bonus to your Armor Class.
You care more about survival than victory.
Prerequisites: Halfling.
Benefit: When fighting defensively or using total defense, your dodge bonus to AC increases by 2.
At the very minimum you are getting
-2 hit
+2 damage
+4 AC