What about dismount? The key that mounts me also dismounts me. Also, mounted I can interact with objects and NPC's, these action auto dismount me. Then entering a building or an enclosed area auto-dismounts me.
I hit RightCTRL to crouch.
While doing anything with keayboard arrows my smallest finger always lies on this key so it's an obvious choice .
PC EU (PL): 14 characters. ESO player since 06.08.2015. Farkas finest quote: "Some people don't think I'm smart. Those people get my fist. But you, I like."