Seems that you have a fairly good grasp of the current LS / MSN situation. Best way to get what you want, is to submit the stuff that accurately depicts your site to LS, and then hope that it gets into a good position :)
Also, if the ROI is there, consider Overture (as that will get you above LS if you haven't already been using them, anyway). Then keep in mind, that for some keyword markets, MSN sells them direct as well...so, if possible, don't ignore that avenue (though I don't have details on that program - and it may get discontinued according to rumor).
Remember to use a tracking url, and cookie the user based on the referrer, so you can measure accurately the performance of your campaigns.