it dosent matter what your doing with it, you would compensate for the worst case scenario, because you can have the thickest sway bars on front AND back and it wont affect your every day driving, because sway bars only come into use on cornering, it wont give you a stiffer ride.
in most cases a thicker sway bar means stiffer, so by upgrading a sway bar it just means putting a thicker one in (correct me if im wrong)
i believe with the bc coilovers you can ask for different spring rates??? maybe your ones just has a softer spring rate, i dont see why you cant go to a suspension joint and ask for stiffer springs to suit your coils.
everyone talks about coils to solve body roll because to an extent a sway bar can help, but the term "more=better" dosent work in this situation, more (stiffer sway bars) will help till you find traction issues, with coils, they work individually and when cornering, one side of coils wont raise the other side, therefor not giving you traction issues.
i have tiens in my car and they are super stiff, and i have little body roll.