I have moved your thread to ClassiPress Feature Request as you're obviously asking for this to be a feature that is not already available.. I don't believe we will see this particular feature however, as the topic has come up a number of times, and really if you start allowing your customers to completely delete their ads, this is going to effect your sites
SEO. Most of us don't want that to happen.. This is why only the pause ad option is available in the customer dashboard.
What will be available in the next version of
ClassiPress 3.1 is a "SOLD" button in the customer dashboard which will mark the item as sold whilst allowing the ad to remain live.
Again, if sold out items are an issue for you, then perhaps you might want to look at ad pruning so that ads expire after a certain amount of time..