As an airport agent at BNA I can attest to the fact that the 1W only becomes available if the back is full. SABRE will not allow us to give the 1W unless all the seats in back are given out...the only way I know around this is to go into the seat map and "block" all the open seats as if they were inop and then give 1W and unblock the blocked seats. I have no problem doing that unless the CA has an issue with it. I have never been instructed not to do it so until then I will be happy to give you the jumpseat when commuting out of Nashville.
Also on the ERJs weight can be an issue and I have been told by OPS more than once that the jumpseat would take us over limits even more so now that people are not checking as many bags thus keeping the C.G. more forward. If I run into this situation I always go down and talk to the CA and they are useually able to work the numbers around to make it happen.
We have alot of pilots out of BNA for some reason (I guess alot of them are left over from the "Hub Days") and I always do whatever I can to get them to work. I just wish AA would start charging for revenue standbys. It never fails that we will get pax buying seats on the last flight to ORD and showing up at the airport at 6am wanting to go early....they know that we don't charge and that the last flight is the cheapest.