I have to second Atlantean here - NO for security as late as possible. Berlin Tegel has that kind of approach, and their post-security waiting rooms are sparse and not all that pleasant.
And Atlantean, please tell me you're not back to flying into CDG are you? I've given up doing the trek to BRU or CDG by plane because the two hours that it takes me from St Pancras to Bruxelles-Midi or Gare du Nord is definitely worth it if I practically immediately get to where I need to be. :-)
S.