when I sell to the public I find Free Shipping is a great advantage.

You must be the first B2B that I know of that doesn't seem to charge shipping (at least under a minimum order amount)

Standard B2B features to me seem to be all about cost recovery

I agree with fairestcape go with:

Minimum order amount.
Freight charged, perhaps Free over a certain amount

I can't see why you offer Free Shipping to businesses for small amounts