Definitely not. Edmund's very much a younger brother; he's meant to be a support system. If instead he's supporting Susan -- well, he and Susan have a very different dynamic, and doubtless he'd be forced into the position that Peter has by default: not the position of High King, but that of general. And while Edmund could probably do it, he's not as good as it as Peter; he's not a natural leader.

It's hard to say, really, exactly what the differences would be. Movie canon doesn't give us a lot of Edmund; it's mostly been about Peter. It will be interesting to see what they do in Voyage of the Dawn Treader.

And if you're looking for good Peter-and-Edmund meta, I recommend cupiscent's, here (http://cupiscent.livejournal.com/457788.html).