I'll be the buzzkill... Grew up in Stillwater and still have a community of family and friends there... I literally never heard of "Okie State" until I joined this forum. "Okie" is a loaded term, the older generation still remembers it being a derogatory term. You can use it but you handle it with respect and know your audience. It's kind of like, I can punch my little brother but you cannot punch my little brother lol
"OSU" works always. "OKState" works in print (OKstate.edu is the college website and on various branding). "Oklahoma State" works always. It's not complicated.
I do love the wordplay though let's be honest. Too bad Okie has other connotations