Just put it to play actually and then tell it again.
Only going to this prestige class is kind of difficult.
You loose BAB, as a small creature you already have -1 CMB/D.
Actually you even get +3 from aid another, because of excellent aid feature and its getting better.
Youre right with the action though. Since you can only use it for:
"giving her a bonus on her next skill check, attack roll, or to AC against the next attack" i dont think its soooo strong. First make that check.
I considered it, but then as a ninja decided i dont want to prestigeclass and be in the frontline that way necessary.
I think it sounds cool but not overpowered. On an opponent's action, you can make a combat maneuver check against their CMD to get a -3 against that action and a +3 to an associated skill check, attack roll, or AC vs. next attack. (The 3 is Aid Another plus Excellent Aid.) The downside is the sacrifice of your next swift action.
I say "associated" because what makes it awesome is that you have to describe how you use your opponent's action to your advantage. (That's why it's an immediate action.) So, you have a mechanical incentive to make your actions more cinematic and interesting for everyone else.
Sadly, I don't have any experience with it in play. My only halfling character at the moment is still first level. However, this is definitely one of the possibilities that I'm considering for later.