You'll get more fullness in the upper pole (a little), but won't get the nipple any higher. You're at the point where that would require a lift. If you don't want the scars, then your plan is ok. Good luck!
If you are debating, I would recommend you do nothing at this time.An implant is going to make you bigger. You are already a D and questioning implants. Even a tiny 200 cc implant ( which is very , very small) will make you a DDSmall implants will have a small diameter and not necessarily give...
They are completely high ridden, the pocket is way to out of the breast anatomic area, in fact your breasts do not looked enhanced as how they should, you should get them revised with your surgeon.