Necro-raising this thread.
I use this method for keeping Hasten and Practiced Brawler on auto on one of my chars, but you don't need to use files.
Turning on an auto power is wonky, in that if you just slap it in there with a movement command it won't actually "stick".
However, I discovered that as long as something is between it and the movement command, it works fine.
So I use these two binds to alternate between the two whenever I move left or right.
/bind A "+left$$powexecauto hasten$$powexecauto practiced brawler"
/bind D "+right$$powexecauto practiced brawler$$powexecauto hasten"
Left sets PB auto, right sets Hasten auto. What you use for the middle command is probably irrelevant, but the timing works, so I keep it like this.
You *can* do it with just the two commands, but the green ring won't stay put. It still fires off, but only if it's usable when you press the button.
Sticking something between them makes the green ring stay put.