But sometimes, these changes make sense. As a example...

Iron Man's armor and abilities could change, and very possibly should, as he develops newer technology and modifications.

The Wasp's costume would change because that's an aspect of her character - a new outfit every issue makes sense for a clothes horse(fly?) like Jan.

Green Lantern could think of different ways to use his power ring, so his capabilities might change (e.g., he might find that teleporting to a location is easier than flying there.) And there's always Mr. Byrne's Mt. Rushmore aspect... :)

Tell me some others. Picks some characters for whom different abilities or costumes (or even characteristics) would make sense.

This GA was very compelling and endearing, and Mike Grell rocked it in ACTION and then over in the revived GREEN LANTERN/GREEN ARROW book, and Dick Dillin also knew how to draw this GA over in JUSTICE LEAGUE OR AMERICA--and I soon discovered Neal Adams' version in reprints or back issues.

So, I loved the liberal, bearded, poor GA, but I imagine that people who grew up on the clean-shaven, conservative(?), rich Jack Kirby version might have been thrown.  But I never heard complaints!  Most people seemed to be of the opinion that the original GA was just a Batman knock-off, so his revamp was welcome.

Likewise, over at Marvel, I preferred Yellowjacket to Ant-Man and Hellcat and Tigra to Patsy Walker and the Cat.  And I was also there to see Marvel Girl/Jean Grey become the Phoenix for the first time.  In reprints, I couldn't stand Marvel Girl's costume (I think it must have looked old-fashioned in its first appearance) but I loved Phoenix!  (Ironically, now that I go to cons, I'm amazed at how good the Marvel Girl outfit usually looks in real life!)  Same thing with Jim Starlin's Captain Marvel and Warlock over the originals (or even Gil Kane's intermediary versions).

So (and this might tick off some fans of the original versions I mention above), if a somewhat lame character is replaced by an awesome persona, I'm more than fine with that!  (Unfortunately, people who AREN'T Neal Adams or Dave Cockrum think they should revamp costumes they gave us--and we're left with Havok in a jumpsuit or Carol Danvers with a mohawk.)

I loved the "spectral, unearthly" version of The Vision. It was a change I didn't know I wanted or needed until after it happened. 

I wouldn't mind the comic book version taking after the movie version more (the best parts, that is; the tiny chest star and weird stomach stripes don't look great) and seeing Steve Rogers' face more for quicker missions or crises that pop up, saving the classic costume for special moments.

Thor could also be given a more majestic outfit (again, the movie version is pretty stylish) as the Kirby design seems too simple for modern tastes (i.e: "the powers that be") and most of the last few decades of redesigns were ridiculous.

HAWKMAN--He could be DC's answer to Wolverine, which I think they tried a bit by giving him claws once or twice; unfortunately, everything else was wrong in those attempts.  At some point, they decided to go with the original (Earth 2) origin with its Egyptian and reincarnation/revenge emphasis--which is good for ONE story!  If they had stuck with the sci fi/Thanagarian (Earth 1) version, all sorts of things could have been done with his uniform, weaponry, strength level (and perhaps new powers), and storylines.

AQUAMAN--Instead of being the laughing stock who "talks to fishes" and nothing else, or overdoing it with the movies turning him into Conan-Namor, a logical look at his origins could give him increased strength, find new uses for his telepathy, and maybe give him other untapped powers.  (Namor sure has enough of them!)  If Mera's water-control powers were somehow transferred to him, he would truly be an "AQUAman" and one of DC's powerhouses.

THE ATOM--I liked the SWORD OF THE ATOM redesign and storyline, but, instead of it being "sword and sorcery" or jumping back to the status quo, what if it was just the START of numerous explorations of "tiny worlds"?  Stan Lee and Jack Kirby gave us an amazing microverse in issues of FANTASTIC FOUR (and Bill Mantlo and co. ran with it over in MICRONAUTS), and I think there are dozens of interesting "microworld" story possibilities that DC has never explored with the Atom.  (AND more DOLL MAN-style fun stories too!)

And instead of reboots, I would like to see these applied to the classic (Earth 1) versions, as their history and experience would help inform these advances.

If memory serves me right, Kevlar Batman came about after the KNIGHTFALL saga. Batman had been broken by Bane, mentally and physically. At that point, he had the blue and grey. Then Jean-Paul Valley took over.

Bruce Wayne eventually reclaimed the persona, Dick Grayson took over for a while - and then when Bruce became Batman again, he had the Keaton-style body armour.

After almost being killed by Bane, and having his back broken, it made sense that Batman would become armoured.

For the opposite presentation, see "V for Vendetta" - where we almost never see Hugo Weaving's face. Probably a good thing, as he was supposedly scarred and burnt in his release, and yet also had an almost irresistible physical attraction. I liked that concept... it fit perfectly.

Of course, in a Marvel cinematic universe where there seem to be no secret identities, losing the mask/faceplate doesn't seem very important.

I am usually of the opinion that if a character has a mask, then his identity should be secret.  So, it really bothered me when Daredevil's identity in the comics was revealed for a number of years.  I think the Marvel moves coincided with a period when Iron Man and others had no secret identities in the comics (whether in the regular line or the Ultimate line), so that lined up with producers and actors not wanting the heroes' faces covered up all the time.  (Even though I think Daredevil and maybe some others in the comics have had their secret i.d.'s restored recently, somehow.)

So, I'm a little torn.  I love Captain America and his uniform immensely, but if his identity is uncovered (I'm not even sure of his status in the comics right now), why keep the mask?  But either way, the chin strap and the chest coins have to go.