Sorry I wasn't able to respond sooner =/
Anyway... in case anyone else stumble into this thread looking for the same thing, I did run some tests and it should work fine. You just need to add another command right after those I described to actually start using the new default pose. So the complete set of commands would be like this:
SetDefaultPose 1 ReidKnight SetDashPose 1 ReidKnightDash SetIdlePose 1 ReidKnightIdle SetPose 1 ReidKnight