"Knowledgeable sources familiar with the WBEN, WGR and WWKB transmitter operations say any thought of moving the WWKB transmitter plant to Grand Island would be very difficult and might even make KB vulnerable to facilities changes for other stations operating on 1520 kHz. KB's 50 kW pattern needs 3 towers to protect other stations on 1520, most notably KOMA."
That may or may not be an issue depending on how you configure the pattern and who you have to protect. If KOMA is the one station you have to worry about, then all you need to do is throw a deep null to the west-southwest in the direction of Oklahoma City, beginning at Oklahoma City local sunset. You could conceivably do that on two, three or however many towers you want in order to get both the sharp narrow null you need, and the gain in field strength in other directions you want. If other stations enter into the equation that may be a different story, but I don't know how stations that started up on 1520 AFTER KB and KOMA established priority on the channel back in 1941 rate in terms of protection.
"As to WGR, it most likely would not be able to run its 5 kW night pattern off two towers. However, WGR could operate with 1 kW on two towers, as it did many, many years ago when TransAmerica owned WGR AM-FM-TV. At that time, WGR was 5 kW-D, ND and 1 kW-N off two towers. The 1 kW night pattern was far less restricted than the current 5 kW night pattern."
Probably couldn't do much to change GR's night pattern at least to the west, where both WKRC and KTRS need protection. There might be a little room to let it out to the east. That pattern, I've been told, was drawn a lot tighter than it needed to be when the plant was built in 1941 because the eastern 'burbs that are being nulled out now were very thinly populated in the 1940s...and they wanted to shoot as much field strength north toward Toronto as they could, because they were Toronto's de facto CBS network source and American stations could make significant money selling ads to Canadian accounts back then. WKBW was made a DA-1 rather than a DA-N facility back then for similar reasons...KB threw more power than absolutely necessary to the east, in order to grab listeners in the western half of the Rochester market at a time when Rochester didn't have a full complement of network affiliate stations (it had only NBC Red from WHAM, CBS from WHEC, and local independent WSAY. missing NBC Blue/ABC, which KB provided until Rochester's WARC/950 signed on as an ABC affiliate in 1947).