Let’s say our septon duo manages to banish Harrenhal’s personal Pazuzu, there is still it’s most practical problem: its size. Can Westeros society find a use for it? I so want Littlefinger to throw open the gates and make it go co-op.

Sure, practically, you should just tear down the thing, make a bunch of money selling excess dressed stone to other Riverlander houses looking to build castles and houses, rebuild it in style, and then get filthy rich building a canal linking the Godseye to the Trident.