What I'd like to see would be a formation that facilitates retreat from battle, or reduces casualties for both so that you have better chances of reducing number of casualties suffered before getting to retreat. Is there such a formation? Apart from, I suppose, choosing limited rather than standard attack mode?
Other than that, just going by intuitive military sense, I've too gone for flank attacks if I have a superiority in cavalry. If I'm significantly outnumbered I've gone for double line, thinking that the enemy will have a longer line that outflanks me anyway, so might as well make it a stiffer line, or assault in depth.