I like, I like. To be fair though, I'm not sure we can say anything at all about these films - I mean is there any substantial evidence that says the sequels will occur after the events of ROTJ, or that they will be sequels at all?
New armor can be made. And a seen where this is happening would explain to viewers that this is not Darth Vader but a pretender - still, it could confuse the general audience.
I doubt Vader's armor could be remade exactly as it once was, given that it also had some sith alchemy in it. But...will see though if it is a pretender, they could have worded it much clearer.