So let's look at this:
You want in advance the other person's PayPal address
This part i don't get.... you ALWAYS have the other person's Paypal address upon payment... i don't see any harm in this.
Just supposing in our example the OP had previously scammed with an Alt account and has kept a record of who they have scammed, by seeing the other person's PayPal address prior to trade, they can cross reference with who they have scammed in the past and "back out" of the trade.