-Don't trade with people unless you know and trust them
-Burden of proof for having to verify that pokemon actually was hacked
-Make your own pokemon if you don't want them hacked--I don't believe that appealing to some morality over programmed bits of data should give the same punishment as someone being malicious to the site.
I think rather than banning users, we use that suggestion of the trade reputation, so while someone won't be banned, they'll have a harder time getting trades organized here.