Yes - I have often found that gate agents can do so much more than you would ever expect. Sometimes it is just a matter of finding the right person. I have had some incredibly good luck.
For example - just last Sunday I was in Houston and booked for a 2:30 flight to PHX, but I was exhausted and saw one leaving at noon. So, I asked the gate agent if I could get standby and she said yes (for a $75 change fee, I had a restricted ticket).
At that same moment another man walked up and said he had talked to the ticket agent (baggage handlers) outside and they had told him that if HE wanted to get on this same flight there was no standby so he had to purchase a full fare ticket, which he had done. He was at the gate to get a seat assignment.
He had done that that before I got my standby ticket, but had to buy a full fare. I only paid a change fee.
There have been other times when I have been told (for example) that I could not get a seat assignment until the flight agents came to the gate desk, but I just happened to find someone at a different gate who happily gave me an aisle seat for the flight I needed several hours prior to my flight.
I have even been bumped up to business class twice (both times on British Air) - without asking.
SO SORRY for your problems however. I admit I did not fully understand the original post, but other people seemed to.