One of the features of the Melee option of Additional/Secondary Attack is that the secondary weapon must be wielded during the use of the style.
Therefore, I would (as a GM), have no problems ruling that you could add a MA Strike as an "Additional/Secondary Attack - Weapon" (i.e. 3 points). The actual Tier of the attack would be based on the character (i.e. humans, elves, dwarves, etc. Would do either a Tier I (at -10) attack if their fist were not armored, or a Tier II (at -10) attack if they are wearing armor on on their fist.
The attack would be limited to the off-hand only, unless the style also paid for "Additional Primary Weapon" (1 more point - and requires the Additional Secondary Attack for the fist).
Okay, so the style would then cost the following:
Single Weapon Focus - Rapier -- 2 points
Add/Sec Attack - Weapon - Main Gauche -- 3 points
Add/Sec Attack - Weapon - Bare Fist* -- 3 points
Additional Primary Weapon - Base Fist* -- 1 Point
Defense Ward -- 4 points
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Total Point Cost -- 12 Points
Bonus to Initiative -- 2 Points
Agile Defense -- 2 Points
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Style will cost 12, 14, or 16 points respectively, depending on whether or not one or both of the last two options are included.
For a Fighter, this means that the style, as listed would have a DP cost of 3/8 (or 4/8 or 5/10 respectively).
* Bare Fist -- The combination of the second
Add/Sec Attack and the
Additional Primary Weapon allows the character to make an attack with their fist in place of one of their normal attacks. The Tier/size of the attack is based upon the race of the character and what armor is being worn. With no hand armor (or soft leather, such as a glove), the attack is Tier I (at -10), if the character is holding a weapon in his hand when making this attack, I would drop the -10 (like attacking with a roll of quarters in your fist). If the character is wearing hard hand armor (reinforced or rigid leather, scale, chain, etc.), then the attack would be Tier II at -10, or a plain Tier II if character is also holding weapon at the time.
The MA attack would have to replace one of the other attacks made during the round. Also, making a MA Strike with the off-hand would negate the Defense Ward, just as attacking with the off-hand weapon would do.
There -- that is how I would piece it together...