Just to be clear... are you saying there is a problem with what I'm proposing?
I'm not sure why there being only 2 fixed 10/100/1000 ports creates a problem. Since neither of them are currently in use and I'm currently only using 2 ports, it seems like my plan to switch from using the fixed 10/100 ports to the 10/100/1000 ports would upgrade my throughput to gigabit speeds, right?