i have had a thought about that and i might have jumped to a conclusion to soon.
i have looked at my spare arms again, and the bracket is quite chunky, don't get me wrong it can be beefed up with a welded plate. but i am worndering if your bracket might have just been rusted away. i only say this due to the other issues you have had with rust, it might be an idea to have a good look at bracket to see if there is any areas of bad corrosion. it looks like the bracket has split right through, the bracket with no corrosion on its about 2-3m thick. so it should in all reality it should be strong enough even for the upgraded anti roll bars.
what i am getting at is if the bracket has lots of rust and deep corrosion on it then a standard arm might be OK for you, as it will not be rusted and you can make sure it is clean before you fit it so a quick covering with stone chip paint of something like that should protected the are for the future from road salt and water.