What no one has brought up (and as a production company that does lighting for weddings, it is interesting that I am bringing this up), but there is a certain level of lighting that would need to be done to make it worth taking the gig. For example 6-8 up lights is not worth it for me. The minimum package I would leave the house for starts at about $1200. Where I think DJs could be valuable is providing the package of say 6-8 up lights on a static color.
Mike
Mike