Recommendation from Darkosto's chat:
[18:41] TheBowAndBullet: Mojang and modders made gates and doors, why not openable windows (swivel in/out, or slide up/down)?
[18:42] TheBowAndBullet: even if these windows require their own recipes, e.g. wood frame with glass
I would love this.
Could act like a fence gate, where it opens from the middle, or like a door. Stained glass too!
Ignoring the rendering funkiness, is this kinda what you guys were thinking https://youtu.be/2eQILHQ9VZQ
Seems I was beat out by insaneau :P
I took a different approach and knocked this up (pending approval): https://minecraft.curseforge.com/projects/openablewindows
Let me know what you think.