Sir Humphrey, in reference to the fences you mention: “If you want a fence it must be not [sic] extend beyond the actual unit area boundary.” It sounds like said fence would NOT be on Common Property and so OK.
Having said that, your approach in OUR strata wouldn’t work. The land grabbers would push and push the envelope until the ugly phrase from Peter Gray’s original post became applicable: “implied exclusive use”.
Common Property, wherever it is, is there for the benefit of everyone and serves to add aesthetics and space etc. even if it is ‘adjacent to a unit’ and ‘nobody else is ever likely to want to use it’.
I’ll never forget hearing a noise in the middle of the night and looking down from three floors up to see our hippy dippy ground floor neighbour starkers on a bare mattress, dragged onto the Common Property lawn surrounded by candles. It was a hot night.