The two stances idea sounds nice, effectively replacing light strike and heavy strike. I'm guessing that abilities like Flurry will become passive and Pummel might switch to a TP buff with a short duration.

Defensive stance: increased evasion, increased counter chance (passive counter that will work like FFXI), increased enmity, bonus damage to "evasion counter attacks" like Jarring Strike

Offensive stance: increased accuracy, increased chance for Flurry, decreased enmity, bonus damage to TP attacks other than evasion counter attacks

All in all, I'm not worried - could even be a huge improvement.