Roger, part of the problem is how seriously do we take the buildup of CO2 in the atmosphere?
Is that more or less important than military surpemacy?
There is also the point that the need to defend mid east oil supplies will go down if synthetic oil is seen on the horizon.
Another factor is that a propulsion laser can only see about 1/3 of the earth at a time. For example, if the Chinese and Indians built one, the optimal place for the propulsion laser is over about longitude 130. From there, in GEO, you can't see any of the continental US, and even Hawaii is an extreme slant.
I like your ideas re multiple people being able to cut them off. Perhaps using a signal that is required for them to opperate at all. To avoid accidental shutdown, perhaps the loss of two out of 7 signals would turn it off.