Uh, you can get Thicket with Martial Stance at any level that Crus.1+1/2 the others equals 5. So, say, at 9. You don't need to take Martial Study, because the prereq. for Martial Stance is just knowledge of one maneuver from the discipline you wish to take.
There is one problem I keep having with Knockback: It doesn't actually stop your enemies from just continuing their movement, and then you don't get another AoO. Also, it's actually pretty hard to knock them significant distances unless you have a means of REALLY pushing your Str and to Hit so you can use big Power attacks.
What I would suggest to include, somehow:
Shocktrooper and Improved Trip. Now you don't trip them with a tripping weapon, you trip them by punting them into occupied squares and get a shot at tripping both. However, this (i.e. directed Bullrush) only works on a charge, IIRC, and possibly on any AoOs you take after the charge, because all modifiers should still apply.