Storing eruption is better for him than the "perks" he gets from NSM imo. There really isn't much of a mindgame to dealing more damage and being a bit faster. With the hitstun as ridiculous as it is, it's easy enough to just combo into a stored eruption from anywhere. That in itself is a better mindgame, because it forces opponents to play more defensively if they don't wanna get blown to smithereens.
I see your point. Though unless you've played Ike as extensively as I have, you won't see the advantages that NSM provides Ike in terms of mindgame. The heatwaves produced by Ragnell during NSM provide a significant mindgame considering opponents need to time their dodges and shields much better, lest their shield be broken after just two well-spaced NSM fAirs. The heatwaves coming from Ike's down and up smashes are deceptive enough to catch targets that try to roll or air dodge out of an attack.
Not to say that I wouldn't rather store an eruption than build up NSM through damage-dealing, but the way NSM is now demands that Ike play aggressively. There have been numerous cases in which I've been able to Zero-Death a player simply because I dealt 75% damage with Ragnell, thus activating NSM and allowing me to use something like Aetherial Eruption or Instant Eruption. Take a scenario between Ike and Fox in which Fox is trying to side-b back onto the stage after an Ike combo. If Ike has an Eruption ready from dealing all that damage, he can easily reject Fox's return with a well-time Insant Eruption.
Add to that that a fAir spam using elfire adds to its spacing/zoning/edgeguarding properties.
I would just hate for Ike to lose the theatrics which he now possesses. It makes him a much more complex character imo, allowing mroe creative play.
I'm all for the Eruption storage, so long as it doesn't take away from his Aetherial Eruption, Razing Eruption, Elfire, and other NSM perks.
I recently read a fan submitted suggestion to changing Ike's NSM so that it is separate from his Eruption charge, and would require his taunt to activate NSM. I'm referring to the suggestion in this link:
http://brawlminus.net/forums/threads/suggested-changes-to-improve-ike.427/
Though considering how the devteam has worked on Ike so far, I feel I've got little to worry about.