Which X-Men characters do you think are in desperate need of a costume update?
By this I don't necessarily mean which characters have the worst costumes (for instance, I hate Cyclops's giant blue condom outfit, but I don't think it's particularly dated). I'm talking about the characters with seriously outdated looks, or characters who have worn the exact same costume for an eternity & could benefit from a redesign.
I think that pretty much all characters need a costume update every now and then so that they would visually always reflect contemporary aesthetics. For instance, Rogue's costume has changed little by little through her character history, which is why I think she's always had a fresh look in every decade. Sometimes, though, characters get stuck with one look that eventually becomes horribly outdated and needs to be wholly & drastically redesigned at some point because there's simply nothing to be salvaged anymore (Exhibit A: Mr. Sinister).
I also think that visual consistency is important. Just because a character gets a costume update, it doesn't mean that everything about the old look should be discarded. Comic book characters always need to carry a trademark visual motif - like a set of colours, a symbol, a pattern, or certain article of clothing - that makes them stand out from others even if their costumes get redesigned every now and then. Boom-Boom, for instance, has had several different looks, but I don't think that her line of costumes has been particularly consistent, which is why she can't be visually all that memorable to the casual reader. However, sometimes a total redesign can be a good idea, too - there's nothing left of the old Frenzy in her current look, which is the best & most memorable one she's ever had. Her old design (skin-tight black leather - how original) didn't really make her stand out.
Anyways. I'll start by adding some characters I'd really like to see redesigned:
Magneto's costume is certainly iconic, but it could and should be updated as well. I think the helmet (obviously) and the cape are his most essential visual motifs, but there has got to be an alternative to the fiercely outdated underpants-on-leotard solution. I think his current look is very outdated, and more silly than imposing. I think he needs to wear something elegantly militant & stately to reflect who he is as a character.
2. Scarlet Witch
Wanda's costume has been pretty much the same forever. I don't think that this costume is horribly bad, but it looks very, very dated. I also hate the pink parts of her outfit with passion. If I were to redesign her costume, I'd keep the corset-like top (though it, too, should be redesigned), and the element of the flowing scarlet clothing (possibly as a long scarf/veil instead of as a cape), but I'd get rid of all the pink, and either change the headgear for something more contemporary or discard it completely. I also think she could use a second piece to her costume.
Outdated costumes seem to run in the family, because Polaris is definitely third on my list. She suffers pretty much from the same problems as Wanda - the headgear and the cape are just not all that contemporary, and I don't know what the hell is going on with that top. Now that she's joined X-Factor her look seems particularly out of place, since all the other characters in the title have very fresh & practical looks. I don't really like anything about the current design, except the colour. And the boots. I'd ditch the cape, redesign the headgear, and completely change the look of that top. Also, I think her costume design has always looked too much like a green version of Scarlet Witch's costume. I wish her look was more individual.
This list is rather Lehnsherr-heavy, but these three are really the ones I'd like to redesign the most. In my opinion, their looks are badly stuck is the past.