Per the PPH, it only takes about 12 minutes to be unconscious after taking the SN. If quetiapine has that sedating effect on you, I don't see any reason why you can't take it (though you should probably take it at least 30 minutes before the SN.
Quetiapine also happens to be a dopamine antagonist (like many antiemetics, including meto). Obviously, it is no replacement for a proper antiemetic, but it may also help to reduce vomiting.
Keep in mind, though, that the benzo is helpful for many things besides putting you to sleep. It is helpful for reducing panic/anxiety around the event (also the SN can cause rapid heartbeat). Quetiapine would not be very helpful for this. You could consider taking a beta blocker, as well.
Obviously, the benzo isn't required for the SN to work - but it makes the process less anxiety-provoking/stressful.