In addition to Matthias Rothkoegel 's excellent response, another option open to you would be to use Eloqua's new feature for Simple Email Campaigns, more info here: Simple Email Campaigns
It allows speciic users to use a simple wizard to easily deploy an email to a segment or an uploaded list without having to create a new campaign canvas, etc. One of the reasons it was built was specifically for your purpose: a centralized team doing more advanced campaigns and automation with canvas and a decentralized team doing one-of localized marketing blasts using the simple campaign wizard. As in Matthias Rothkoegel's suggestion, you could use permissions to control the their level of control very granularly if you like.