Anyone outside of SA doesn't know what a maisonette is btw, modern name is 'duplex'.
You can't knock down and redevelop them
If you want to reroof/paint/do other outside work you would be advised to check with the neighbour first in case they object to your colours
If the neighbour wants to do same you may find they want YOU to match (grandmother had this issue, fortunately the neighbour was so anal about it he actually rendered and painted her side of the house too)
The ones in the country or even older suburbs tend to be on extremely deep but narrow blocks so you can't usually develop hammerhead/unit at the rear style because of the frontage, but you can do it easily if you get the pair
Also the old ones are just generally small pokey little things
Ex-trust maisonettes are
everywhere in SA. They're enthusiastically knocking them down in pairs all over the place, in Whyalla there's a crazy number of them for sale (I swear half of Whyalla is maisonettes) but even more are being knocked down and 4 homettes being built where the original pair was. The trust was leaving one half vacant for years while waiting for the other half to get empty before they'd knock the pair down so you'd get serious vandalism of the empty half.
Oh yeah, its also not good for the value/rentability of your half when someone burns down the other half. Which happens surprisingly often in the areas that have those old maisonettes in.
Modern duplexes are a bit different just because they tend to be on much smaller blocks so you couldn't develop them if you wanted to so that removes the temptation, and they are MUCH bigger inside than the old ones.
