^ I think if the Breen got any collateral results from their subterfuge activities they would have been happy with those as well. That wormhole ship was like the pearl of great value that they were willing to do anything to get it. Sure the androids were a great resource to have but the Breen leader thought the engines were a greater tactical advantage. And for all we know, they still have some of the androids left.
As to everyone saying how stupid the plan was, many Breen agreed, which is why there was a change in leadership. However, had his plan succeeded, he would have been highly regarded by his people. Fortune favors the bold but sometimes the bold die or come back empty handed.