L.A.: providers get two ads per week, not one. And can advertise in up to 5 cities. (Although that's mostly for touring ladies.)
But if you think about it: every post is an ad for a lady. Sig lines, threADs and other such all add up to exposure (read "advertising") for a lady. So long as she's not a foolish PR nightmare, it works.
hotindallas: no, ladies may not use ISO as yet another ad forum. They may respond to ISOs (another public advertisement) but can't start a thread like the one you described.
Anyone who thinks ladies need "more advertising space" hasn't really looked at how the board works. If you aren't making it because of the ad guidelines, I'd submit that something else is wrong with your business, not the amount of ads you post.