popmuze, I can sort-of understand why you're suggesting this: but the thing is, it gives you no advantage.
At best, all that's going to happen is the requesting agent you grant the exclusive to is going to say ok, and then read your ms whenever he or she gets round to it. The exclusive thing is not likely to get them to read it more quickly. All it's going to do is prevent you from sending it out anywhere else until the exclusive is up.
They might well read your response, think you're being snippy, and send you a form rejection. Or worse, perhaps, delete your submission and not even let you know they've rejected you.
At best, all that's going to happen is the requesting agent you grant the exclusive to is going to say ok, and then read your ms whenever he or she gets round to it. The exclusive thing is not likely to get them to read it more quickly. All it's going to do is prevent you from sending it out anywhere else until the exclusive is up.
They might well read your response, think you're being snippy, and send you a form rejection. Or worse, perhaps, delete your submission and not even let you know they've rejected you.