IMO, 3rd base is way off base.
Pulling air theu hoods is the CORRECT way to cool lights. Period. No debate or even a friggin doubt.
As far as heating up your fan because of the temps of the lights??? what r u talking about? That is completley false.
Modern hoods seal quite nicely. Back in da day, we would have to sael up the lights with that crazy silver tape, no need for that anymore. Most all new hoods I see are self sealed.
There is no need to split off either if you are just cooling say 4, 1000 watt lights. If you have aircooled hoods, and install hard elcows at your 90degree turns, and use insulated ducting and keep your ducting runs tight and to a minimal, you will have NO issues cooling 4 lights with an 8" Can fan or equivilant. Trust me on this.
If your gonna play the game at this level, money spent should be no issue.
You need your light exhaust SEPERATE from your room exhaust. ONLY the room exhaust needs to have a Carbon scrubber installed.
That brings me to the point of ensureing that your light loop intake is pulling air from OUTSIDE the room. No need for a filter thus no big CFM "drain" from ahving to pullthru the filter, then thru your lights.
I know some of you fellas sare going to think I am full of it. But this is coming from someone who has tried every method twice.
If you want cool temps on your lights aand your room, pull air thru your lights.