My biggest concern right now is the effect customization will have on competition. My concern is not about balance, but whether a huge part of the game will be meaningless. I liked variations, even though many were forced, because it was all available competitively. So much of IJ2 is just useless to me, regardless of how cool some of the gear/abilities are, because any skill shown using these features was suspect. I'm hoping customizations is something that is meant for the competitive arena. Perhaps something that is done after you pick your character; for instance - you have XX amount of some currency to adjust/choose some options/abilities to go into the match with. Each character would have their own list of options that would be the same every time. Perhaps some options would be locked at first, but the implication would be that in competitive play, all would be available and constant (Basically what variations was, but having the ability to fine-tune individual strings/specials). If its anything like IJ2, I'll be quite let down.
I also want to chime in on the *running* debate (no pun intended). I am surprised that so many people are against the run button. I find it to be too important to mortal kombat to get rid of it. If the problem is unfairly quick pressure, then something creative can be done to limit that. Exploring the options opened up by running, and run-cancelled specials especially, were some of the most enjoyable moments I had with MKX. I'd be OK with a slower run, or perhaps more heavily reliant on acceleration. However, I would think that dash-cancelling attacks might be needed to keep the natural MK pace if running is greatly diminished.
