My goal for each of these games is to offer some rules variations you could (but don’t need to) use with the other games if you want. So no, I haven’t revised any of the earlier 2400 games to use the Legends armor rules, but yes, you are absolutely welcome to replace the other games’ heavy armor with how heavy armor works in Legends.
I am not sure what you mean by an armor saving throw, but my general philosophy is to not add extra rolls when playing 2400, if I can help it. I’d personally rather just say that some armor obviates the need for a roll at all, or makes if so the risks of a roll are less (like “get hurt” instead of “get killed”). The rule about breaking armor is designed mostly as a safety tool for players who worry about losing characters, but it’s also inspired by real-world ballistic armor (and bike helmets!), which does indeed need to be replaced after absorbing a potentially lethal blow.