I don't like this idea.
Unless the group owner is capable of making userbars in their own time, how else are they going to find one in such a short time frame?
For example, Little Jimmy wins a 24 hour userbar change. He then has to get another free userbar from somebody willing enough, within that short time frame. Do you really think he'll be able to find something decent for free in such a short time?
The only way I see this suggestion being of any use is if the "perks" were permanent. Any temporary changes would not increase the value in any way, and would only confuse the fuck out of people.