Remember, we have an SGL that can rush the UN. If Saber inflicts enough damage on The Council, to the point that a Saber victory looks imminent, then we expect The Council to vote for us in the UN, so as to deny Saber the victory.
We will have to alert The Council about the invasion fleet, though they should be able to see this force on their turn (air patrols).
I had not considered a Marine Army. Saber has built two Armies in recent turns, so two Marine Armies are possible. That would be four attacks (two for each Army) so they must have more Marines on board the transports.
I am sure that Saber loaded their transports with the knowledge that if we saw them we would tell The Council. So even if The Nursery is reinforced, Saber will still attempt to invade. To them, there is no other option.
Has anyone been able to verify the drop in prices for stealing tech that Saber mentioned?