I'm not too fussed about having actual numbers of figures on the base for BA. I use a lot of DA BA, which have 1-3 figs per base, and when I'm using IWM or kitbashed BA I'll often use a half-hex. Helps that I use a lot of plastic hex bases (from RPE or Chessex), which are easier to halve than IWM metal.
I'll typically put one assault, two heavy, or two-three medium/lights on a half-hex, but it depends on the figure - the DA Salamander is too spread out, so it'll either be one per half-hex, or two on a whole hex. Here are some examples:
This economises on BA figs, and also allows two BA units to fit in a standard hex, as per the rules ;)