APG1 has a new Stunning option for Change Environment you should check out. I've posted more details on older threads of similar topic.
[Notes: From APG1 page 83 - The Stunned effect lasts as long as the Change Environment is maintained (1 Turn*). However, when affected the victim gets to make a CON Roll immediately (at -6*), and if the roll succeeds the attack has no effect on him. If the roll fails, he gets to make an additional CON Roll every Phase he's affected at a cumulative +1 (so +1 on his second roll, +2 on his third, and so on). As soon as any roll succeeds, the power immediately stops affecting him and he has his full Phase in which to act.]