Even though she never actually became an official Legionnaire, Laurel Kent remains a popular character. (Maybe it was partially due to her costume -- or lack therof.)
I believe Laurel wore her trademark "cape-poncho" over her skimpy black "costume" during off-duty hours. It certainly would have been an impediment during flight. And while invulnerable Laurel didn't really NEED much clothing for warmth and protection, I always wondered if her bare feet occasionally ran afoul of the 30th Century's equivalent of the "No shoes, no shirt -- no service" policy.
As for the Manhunter retcon -- most Superman fans know that the Byrne "Man of Steel" reboot declared that Superman was the SOLE survivor of Krypton. this meant the elimination of Kara Zor-El in the Crisis, no Kryptonians in Kandor, etc. But to further make Superman unique and alone, another mandate held that he could not father progeny -- Superman was also the LAST Kryptonian.
Now, this does make scientific sense since there's no reason to expect that humans and Kryptonians can cross-breed, or that any resulting offspring wouldn't be sterile (such as mules). But if Superman cannot leave progeny, that in effect destroys Laurel Kent as a descendant.
Sure, we could have retconned Laurel just like Power Girl -- she only BELIEVED she was related. But apparently DC was ruthless in pruning ALL connections to Superman, and so Laurel Kent was "retconned with extreme prejudice".
Now the Laurel Kent Manhunter said she infiltrated the Legion from the beginning, so how does one explain Laurel's shooting? Certainly the doctors would have immediately noticed. ("Strange, her blood has all the characteristics of transmission fluid.")
My take on this is that the Manhunter lied to the Legion so they wouldn't search for the REAL Laurel Kent. The poor girl was probably abducted and replaced with a double shortly after the assassination attempt. Whatever happened to her afterwards is in the realm of fan-fiction.
And if you want a "Laurel Kent" analog in the new Legion, remember that "Superman's daughter" Cir-El jumped into the timestream in Superman #200 to "erase herself". But since even Superman with outside help didn't QUITE get back "home" (thus the Birthright origin), is it that unreasonable to speculate what might happen if Cir-El took a wrong turn and emerged in the 31st Century? Horrors.
One might suggest that the Legion writers never truly forgot Laurel Kent. Perhaps the addition of Richard Kent Shakespeare after the Five Year Gap was a partial nod to Laurel's origins as a possible Superman descendant -- remember, one of his primary powers was invulnerability.
And then there were the Laurel Gands (Five Year Gap, Batch SW6 and Zero Hour Legion versions), who were more of a replacement for Supergirl but retained the "Laurel" name.
Recently we saw a Laurel (Kent?) Superwoman in Superman/Batman #23-25, though she and the Helena (Wayne?) Batwoman were probably only Mr. Mxyzptlk's creations.
And though it's not in mainstream continuity, in Justice League Adventures #28, some JLA members are transported to the 31st Century. Afraid that these legends might cause a riot if seen by the public, the Legion quickly disguises Wonder Woman as Laurel Kent (minus the "S" shield), and Hawkgirl becomes Dawnstar! Even Kent Shakespeare makes a cameo as a reporter. Lots of fun in that issue -- Laurel Gand also appears as Brainy's girlfriend (she seems to be more closely patterned after the SW6 version rather than the xenophobic "Archie Legion" incarnation).