Title says it.
Any plans to provide the ability to sell text ads by clicks and by impressions as well as by time? Expiration would then be based on 1 of those 3 (whichever the advertiser purchases). I would imagine that most text advertisers would prefer to pay per click or impression VS time.
It would require tracking for those links which would then make it convenient to display tracking data to the admin and to the advertisers.
Would be worth well more than your current asking price if you implemented those features.