I've made 20 batches in an un-modified cooler by sparging in my bottling bucket. I did use a copper tube that goes into the spigot in the bucket, across the bottom, bent 90°, then a clamped on mesh. I drilled a small bung to hold the tube in the spigot. The tuse goes all the way across to help retain it in the spigot, can't accidentally stir it out. I use a 4qt sauce pan to ladle the soup into the bucket. Oh, I line the bucket with a paint strainer bag from Home Depot.
My recatangular cooler is a size smaller though. More efficient that way. 34 qt? I've done 15# of grain in it, which fills the bucket to the brim. Oh, pour in some of the 176 water first, to pre-heat the corners. The inside are buckling just a bit after 20 hours at 152.
So far, I've had more experience thinking than I've had brewing....you don't think they are mutually exclusive, do you?
57 batches so far,
33 wine, mostly Loquat, peach, plum, prickly pear
22 beers and ciders
1 Tequila, from a prickly pear wine experiment that didn't work. I call it "Prickly Heat"