I also posted this here: https://www.reddit.com/r/minecraftsuggestions/comments/tgki53/mounted_spyglass_a_fun_way_to_show_off_your_builds

Tower viewers are those mounted binoculars in tourist attractions. They overlook beautiful landscapes or monuments, and let you see them from a distance. Mounted spyglasses would do the same thing.

Builders could add mounted spyglasses to an observation tower, drawing attention to something they're proud of. Adventure maps could use them to point at hidden rooms. They would make a nice astronomy themed build.

Mounted spyglasses would be a block version of the spyglass. Right click to zoom in where the spyglass is pointing.

Normally it will remember where it is pointing after the player closes the interface. If given a redstone signal, that direction will be locked in. A weak redstone signal will make it snap back to its saved direction when the player closes the interface. A max strength signal will stop them from looking around at all.

This might fit Supplementaries more