I am not in any way suggesting that I might do this nor am I sure that it would even work, but I can't figure out a way to google the question
Suppose that you have a house with a largish attic and you put a downdraft cooler in the attic at one end of the house with the vent thru the ceiling. You could just open windows, but what if you put an "exhaust" vent in the other end of the house. At this point you could leave the attic with proper ventilation and you might get some extra cooling from the exhaust of the cooler. Or you could "unventilate" the attic and the air would continue to recycle.
Thoughts:
with the unventilated attic I suppose the humidity might build up.
the exhaust vent could allow for a filter that might provide some air quality benefits
with a little bit of extra work, you could place the swamp cooler in the middle of the attic and duct work it to the vent AND with the addition of a split duct and controllable gates you could vent the second duct to the exterior of the house and use the cooler with water off at night as a whole house fan. This would make the whole set-up useable for more hours per day
So I know I've missed something here and I know there is an increased leak/water damage risk and who knows maybe a permitting problem, but are there any major flaws in this?