Metamagic used to be feats. Meta-fighting also tends to be feats.

Feats aren't a great way to do this.

With the new Skill attribute, there are a lot more options. Consider:

Fighting

Skill 0

• Disarm
• Grapple
• Trip
• Charge

Skill 1

• Parry
• Dodge
• Block

Skill 2

• Power Attack (suffer AOO, add damage)
• Cleave
• AOO

Skill 3

• Riposte
• Revenge

Skill 4

• Knockdown

etc..

Magic

Skill 0

• Extend
• Enlarge

Skill 1

• Dispel
• Counter

Skill 2

• Widen
• Empower (?)

Skill 4

• Chain

etc