You simply aren't going to be allowed to sign for your wife in your divorce.
There isn't a judge who would allow it. She could have begged that you sign for the divorce, a judge still won't allow it.
You aren't going to be able to cheat your wife out of her share of the marital assets unless she gives it all to you. And for a judge to accept that, there has to be full disclosure and SHE HAS TO PERSONALLY TELL A JUDGE THAT IT SHE DID INDEED SIGN THE AGREEMENT AND THAT SHE FULLY UNDERSTANDS WHAT SHE IS SIGNING AWAY(after being told that she may have done worse or better had the decision been left up to him. And if there isn't an attorney present for your wife, the judge just may tell your wife what she is legally entitled to).
One day, your wife will get fed up. And you will have to pay her for her share of the marital assets.