So, this might sound ridiculous (good way to start a post right?), but I will keep it short and sweet.
I think a good compromise, or incentive, for the rooftop owners is if they make the proposed scoreboard double sided (if possible). The rooftops will still have a view of the field, albeit limited from what they are accustomed to, but they will have a GIANT video board to view during the games.
Imagine a playoff run? People would be flocking to those rooftops and streets to be "there" and have the video board to view. This, as I see it, will bring equivalent profit to these specific rooftops and may even give them more business.
I know it would be a lot more complex than my simple idea here and there are many flaws, but I feel this would be an interesting twist and the video board can be the first of its kind.