There's a multitude of bugs surronding the settlers defense mechanic and power armor usage (the guards always leaves the guard post, they take power armor and leave it any f*#@ing place or die with and you can't get it back, all of them leaving the protection of the wall to chase enemy instead of letting the turret do the job, ect...) I think a mod correcting a few of these issues would be nice. Assigning a settler to a power armor would a good way to correct one of these problem.