Have you seen bank "login redirects" when the system redirects you for ca. 5-10 times before actually letting you in? This proposal could be defeated in the same way: after successful authn, the user is redirected to the page '/wei_chk_1', then '/wei_chk_2' and so on until '/wei_chk_$n', e.g. 10 or WEI check success. If the WEI Javascript check succeeded on at least one page, you are logged in. Otherwise, get lost.