Lord Pendragon said:You're missing the part where the feat can be taking multiple times, and its effects stack.
No, you're making the same mistake everyone else, looking at the FEAT and not the ability of the Enlightened Fist. The Arcane Fist ability is what I quoted, the Rapid Stunning feat is useless in this argument if the DM takes the Arcane Fist literally and states you can only use Arcane Fist once per day.
Basically, take as many stunning attacks as you want, but only once per day can you substitute a single attack for the Arcane Fist ability.