I don't have the ACG myself yet, but if that's the exact text for the capstone, it could be easily interpreted as to gaining any number of feats. Especially since I've seen somewhere around 8 people who've made similar posts so far.
They haven't been fully quoting it.
Martial Flexibility wrote:
At 20th level, a brawler can use this ability to gain the
benefit of any number of combat feats as a swift action. Each
feat selected counts toward her daily uses of this ability.
So at 20th you can gain 13 combat feat at once. For one minute.
Now, go look at the Martial Master fighter archetype.
Depending on if Chosen of Iomedae can be modified a little, (Changed to Sarenrae and to a greatsword instead of Iomadea and longsword) I'll go with Sarenrae, otherwise I'll change to Iomedae for my paladin.