The seller signed up to pay X commission when he listed, right? So I guess the downside to using a lawyer to write the offer for a flat fee is not potentially getting some of the commission in rebate form thats going to be paid anyway. No?
However, I guess you could use the lawyer, submit a lowball, note in the offer that there is no commission to be paid to any buyers agent thus the # is low, and thereby put the screws to the listing agent to cut his client some slack to make the deal happen.