My motion on this will be a "No".
Hiring participants in a signature campaign is correctly in that section along with people offering their services. New posts in the campaign threads are always vital information and by no means they are burying other people's threads. It is just how a forum works.
Exchanges, Mixers use the Service Announcements section but freelancing jobs should be in Services itself.
A signsture campaign doesn't fit the strict definition of a service that would be advertised via a job and. Job ads posted in service boards are about individual positions or tasks. A signsture campaign is what is says, a campaign. It is a very different nature of thread and honestly skews the visibility of normal [HIRING]/[FOR HIRE] posts in a service board. For the latter, the individual posting can only post once every 24hours in his own thread, for signsture campaigns, which we have dozens of, participants are forced to respond and therefore hide threads by individuals.
If your worry is remaining within the confines of the services section, sorry not, because bircointalk's software allows to create sub-boards.