To the OP, i think groogy method would be good. You can create a 2D scene graph to represent your aircraft. So you have something like
Aircraft
/ \
Front wing Back wing
hardpoint1 hardpoint2
When drawing, you just need to tranverse your aircraft tree and draw respectively.
I do not know how sfml really batch their sprites, but if you are going to batch your sprites, it doesn't really affect if you draw 3 extra sprites or anything. For your record the the amount of vertices being push to the GPU every frame is in the order of mbs. My vertex cache is 32mb big for my game and I push them into the GPU in blocks of 8mb, so your few extra sprite is not going to really impact your game much. Don't worry too much =).
regards