The board members look like they have been there for a while. The man who seemingly was helping Nagisa looked like a veteran in that business, being the vice president to boot. I find it exceptionally hard to believe that if they really were stout and smart enough to be of any use against Kazuhisa out of their own volition, not only as tools Nagisa would need to prepare slowly and carefully (like Kazuhisa probably has), they wouldn't have needed to wait for Nagisa all these years. They were just paper tigers. I doubt it would have made any difference whatsoever if Nagisa had worded his message differently and only talked about A-Tec. Kazuhisa must have seen through him a long time in advance.

Hard to say about Kazuhisa and Iris. Wasn't it the Kiryuus who slew the Shinamiyas? You'd think Kazuhisa would have got rid of Iris for good if he knew. Apparently Iris is living as an orphan and is a pilot, so it would have been easy enough to arrange an accident and have nobody important miss her. On the other hand Kazuhisa looks even more than Nagisa like a man who imagines he's in control of everything, so I suppose he could be keeping Iris alive out of arrogance. However, it seems quite unlikely he would try to elimate her by removing A-Tec. Sure, it might push Iris farther away from the company, but it would also mean he might not be able to keep an eye on her.

A shoujo show theory: Maybe he wants to marry Iris and is keeping her live and close because of that? Now that she's getting old enough, it would be the time to get rid of A-Tec. Haha.