No way! Of course not! That's the point of designing--so you can tailor it to what fits you!
I' *don't* know how to add darts, though.... I've only done bust shaping with shortrows (and then subsequently frogged because the whole thing was too big anyway).... :thinking: hopefully someone else will be able to help in that area.
cables WILL increase the amount of yarn you use... and cables also make a thicker (warmer) fabric; that's why it's used in all those Irish fisherman sweaters.
I'm not a lace afficianado..... Part of me wants to say lace will use less than average because of the holes.....