Ivan, as Eugene said, self squading could work if they locked in the team times and slots. Then left the rest open. It is done this way at much larger, more complex matches all over the world, no reason Canada can't figure it out. The match director always had the option of moving people as necessary. This actually makes it easier for the MD and allows people to make plans ahead of time, planning carpools, flights etc. Why someone would not want to make things easier for the MD is beyond me.
As for working while shooting, it is definitely personal preference, for locals it's better, if they know ahead of time when they are shooting... for me, flying in and having to be there for the whole thing, I'd much rather work a half day or more than doing it while shooting. Especially when there is an "off" day. I like to be able to focus on shooting and not worry about catching my gun on a popper, or prop when setting stuff, or being rushed in cleaning my mags because no one else is patching. Hell I'd pay extra to not have to work at all if the price was reasonable. If people like patching or painting while shooting I'm sure no one will stop them from doing so during the time on a stage. I also think stages run better with dedicated workers than with new people every squad. Less mistakes, less confusion and smoother flow, typically.