When turning in thieves guild jobs you will usually get a pardon, which will help alleviate any bounty you have on you. What I would like to see would be a chance to instead of getting a pardon edict you could get something to reduce the number of fencing slots you have used. Maybe call it a Note of Favor. You have come to the attention of a local fence who is willing to do move some extra goods for you.
When you use it it would reduce the number of fence slots you have used up. So once I have fenced my max of 140 items. I could use a note and get back a random number of slots, say from 20 to 40. This would allow me to continue my thieving and fencing for a few more jobs.
Just a thought. I enjoy the pickpocketing jobs but quickly run out of fencing slots.