I can't accept that 540 is at a serious disadvantage versus 580.
Yes, it doesn't go quite as far north as 580, but that's only an issue on the fringe. Remember, the metro is only Orange, Seminole, and Osceola counties. Not even Lake although that may change someday. In other directions, the coverage is equivalent. 540 is a laser-beam into downtown Orlando.
At night, the coverage map shows the interference-free zone (14.9 mV/m) as a relatively small strip of land in Orange and Seminole counties. But I think that map is conservative, perhaps assuming a higher level of interference from the Mexican clear than is truly the case in the real world. I've been able to hear 540 after dark as far west as I-75 in Wildwood, which should be about 3-4 mV. They seem to have heavy processing after dark that makes the audio sound robust compared to the background noise.
I think the concern about narrow-banding on the analog is misplaced. Many low-band AMs sound a little bassy or boomy because the higher frequencies are a higher multiple of the center carrier. Once they go HD, that won't be an issue as I'm sure they'll retune the array as necessary to pass IBOC.