Cool Ranch Doritos are basically corn chips with ranch dressing flavor sprayed on them, right? Why not throw a packet of
Hidden Valley Ranch dressing powder into the secondary? Maybe with some dehydrated polenta or corn grits to impart a corn flavor without all the oils and stuff in tortilla chips.
If that works (and I'm not saying it will, but ...) perhaps a Nacho Cheese Doritos effect could be achieved with
Kernel Season's Nacho Cheddar popcorn seasoning? They sell this stuff at Target, hereabouts. There are other brands of nacho cheese popcorn flavoring.
I'm curious if this would turn out. The drawback might be that the stuff tastes fake or weird in beer, since you're basically throwing in little packets of artificial flavor and additives. Just like the powder on real Doritos.