How did Saazbaum know Slaine knew of the princess being alive though? I don't think Slaine ever mentioned it to anyone except the King. I find it more convincing that it was just coincidence and human discrimination, even if it is indeed a bit lazy.
I think this was what she implied when she said she didn't want to get dragged in. Rayet simply didn't know how anyone else would use the information. If they did try to communicate it, chances of what you mentioned are reasonably high enough to avoid doing so.
I don't think the soldiers were being idiots. They were surprise attacked during a cease fire by an over powered enemy (that swats hundreds of bullets with a sword LOL). I don't get how you can see that as being idiotic. I would think that a trainee managing to come up with the idea of the armor, pull it off with his piloting ability, then decide to tilt the ship so both machines fall into the sea, and have the courage to risk not being able to eject on time and dying, and do the same shit almost every episode, is NOT being normal.
Inaho isn't anime super genius maybe, but far more than satisfactory in a more realistic setting.