phranque - 11:45 pm on Apr 20, 2013 (gmt 0)
an internal rewrite to a minimal and minified static document as lucy24 suggested would be the best solution.
however, the bots may see a blank page as just as much of a kiss-off as a 403 would be.
it might be better if you had "some" content but still keep it small.
no images, no external styles or scripts.