About the Rectangle Shape... You have something all other body shapes don't have an envious overall proportion!  You have great hips, balanced thighs, shapely legs, amazing arms, and a body frame that's perfectly in line with each other.  A problem you may encounter is developing obvious curves into your feminine shape.  Your neck is short with fullness at the nape, your bust size is moderate in comparison to your whole body and, because your rib cage is more pronounced, forming a defined waistline may prove to be more difficult feat for you.  Also, your derriere is pretty average (and that's alright!) so your body proportions are paralleled nicely with your moderate thighs and slender legs.
Keep working your envied overall proportion and update your wardrobe with all the exciting new trends.  Say goodbye to old styles and hello to your desired rectangular shape!