I say this with absolutely no authority, but if it were me, and I was riding in those temperatures, I wouldn't want to do anything that would possibly block any sort of cooling to the engine, which is right behind that vent. I'd suggest hanging your backpack from the dash hook (you might have to rig something up to make that work), using a bungie net to put it on the seat behind you, wearing it, or putting it in a topcase or carrier of some sort on the back.
That vent does next to nothing. The scooter draws air from the right and it blows out below and left of the engine. If your worried buy a remote oven thermometer($10) stick the prob under the pet carrier and do some before and after testing.
On second thought I think the purpose might be to cool the air between the valve cover and the plastic cover itself, to keep it from getting too hot. Only one way to find out.
