I think that the NFL should disallow icing. It's stupid and ineffective, anyway, but moreso, it extends the game by and extra few minutes. Games are already too long.
I would make the rule that you aren't allowed to call timeouts in the FG formation once the offense is set, but it's up to the referee's discretion. If it's a rushed FG, then the ref has the ability to allow it to let the defense catch up. But on a full play where the defense is prepared, no timeout allowed.
I like where you are going Dave but you can't leave it up to the ref's discretion. That is a disaster waiting to happen. Easier thing to do is have it be when the play clock is under 15 or 10 you can't call a timeout. So, it still gives a coach the opportunity to call one just not at the very last second. And it gives the offense the opportunity to snap it before the 10 or 15 second mark to maybe catch the other coach off guard as he is waiting for a certain moment. I think that is fair to everyone. But, either way I have no problem with coaches doing the "icing thing" honestly. Because it makes the coaches look stupid if it doesn't work (like yesterday). If I were a coach I would just always call it or never call it that way you don't feel foolish if it backfires. You just say "that is our policy"