Victor ... I see the problem that while it is very viable to use the on-board as a trigger for a remote flash there is the hazard of other photographers pre-triggering the remote. This possible problem is overcome by the use of closed circuit systems such as the Wizard ... the problem remaining is that to use the Wizard it sits on the hot shoe and all cameras I have encountered will not raise their on-board when something is in the hot shoe.
I belive some cameras have a PC socket as well as a hot shoe which might permit the on-board to raise itself and work with the 'wizard' thing attached to the PC socket .... but I have not seen this suggested as an option. My experience of trying to run two flashes off a single circuit was largely unsatisfactory when I tried this over 40 years ago and hopefully things might have improved by now ... but it is quite likely they have not with Wizards capable firing several remotes.
That brings us back to having a strobe on the camera fired by the Wizard in addition to the remote. An unsatisfacotry situation from a weight POV and not having the 'fill' flash as close to the lens as the on-board is.
Red-eye is a red herring IMO in this discussion for reasons outlined earlier.
I hope this explains my situation better Victor
Quite academic in my case becuase I will not be shooting any weddings .. that is ancient history for me