Had a new scenario come up last night in a game. I hunted through the wiki and the rules don't have much to say about this situation: A Reverend Moira staring down a Kriigel Agent is activated. The first short skill is Idle. Kriigel declares ARO with breaker combi. Clipsos reveals from Hidden Deployment in a way that completely blocks LOS to the Kriigel and ARO's with boarding shotgun. How would you rule the rest of the order? Can the Moira shoot the Kriigel, or vice versa? We'd ruled on the spot that the Moira could only shoot the Clipsos and that the Kriigel's ARO is spoiled.
The game's rules are written such that in general you can't fudge with the LOF of units in the middle of an order. Strictly speaking, however, LOF is a requirement for BS Attack and the Clipsos will block the LOF to the Kriigel so the Kriigel's attack should, RAW, be negated and turn into an Idle. The Clipsos also can't Dodge or Engage to prevent this LOF blocking due to the FAQ.
You check for validity of an order at the resolution step, so although at the time that the Moira Idles (with it's first short skill) the Kriigel has LoF and can ARO, at declaration (after all AROs and skills of an order) the Kriigel no longer has valid LoF. End Result: The Kriigel reverts to Idle, the Clipsos shoots the Moira with a BS, and the Moira cannot do anything that hits the Kriigel (unless it does not require LoS). Of course, the Moira player, being a tricky Nomad, would know they couldn't hit the Kriigel directly, and so unload into the Clipsos instead (and I hope they've got a Shotgun, or some direct template weapon to do so with!).
I strongly disagree with the two posts above. Yes, you check Requirements during resolution, but you're checking back across the entire Order so far, not the specific situation at that point. As far as I'm concerned, the Moira and the Kriigel had LoF during the Order, so they both get to shoot.