But casual players are exactly who this isn't aimed at. A casual player when presented with a $20 used copy of the game, and a $40 new copy with enhanced features, will more than likely favor the cheaper version. Why? Because as you say, they won't notice the balance or netcode, nor will they likely play the game long enough to appreciate the new characters.

As to balance and netcode, these are exactly the sort of things that capcom should be giving away for free, simply because the new network and update systems of the next gen systems allow them to, and the fact that they need fixing at all implies that they didn't test properly in the first place. The attribute and frame information that would be tweaked in a rebalance likely make up no more than a few megabytes. It should be a cheap and easy fix. I believe that other games have already done this. I want to say that armored core 4 did it with their regulations file, but I'm not 100% certain there.

I understand Capcom wants to make a profit, but I really feel that they should adapt to a changing market rather than putting the screws on their fan base.

I'm all for supporting Capcom, but honestly I expect the company to support itself. I expect it to make product that people want to buy. If it has reached a state where the only way it can continue to exist is to nickel and dime it's customers until even they will no longer support it, then... stick a fork in it, it's done.