I'm not sure if that's necessarily the right direction. Make Karen serious.....like 90% of DC's other books? That's not going to help her stand out or stand on her own, it'll just make her book redundant. No, I think the best option for PG is to provide something different. And that could be any number of "serious" things (multiverse travel, corporate heroics, etc) but providing a different subgenre (comedy, horror, retro pulp, whatever) shouldn't be taken off the table just because Karen needs feats. In her last solo she held up Manhattan island. That's a damn impressive feat (don't pretend its not) and it happened in a book that didn't take itself too seriously.
And yeah, a love interest isn't terribly high on the priority list. I can think of three other things just off the top of my head that would have to be considered before the supporting cast. But Powerwing would offer some really nice benefits that Karen could take advantage of.
First off, Karen's unlikely to get another solo. It *could* happen (I hope it does!), but the odds aren't great. She's more likely to be on a team like the JSA, where character development and subplots have to be spread around the whole roster. Which means there's not much room for Karen to shine; she'll get her 15 minutes eventually and then the other team members will get their's and in a few years Karen will get her turn again. As a major supporting character in Nightwing however, she'll have more panel time, and we all know that a love interest's subplots/panel time don't always have to be about the relationship. Good love interests get developed as well rounded characters with their own lives. So this means more panel time for Karen, more development as a character, and a second book for her to appear in on a regular basis. It's win-win-win.
It also gives her strong ties to a major character that'll actually use her (unlike Superman), use her consistently (unlike Harley) and makes it less likely that she'll end up in limbo. Hell, the only reason she's shown up anywhere in recent years is because of Harls. Obviously, looking at Nightwing right now a Powerwing relationship is no guarantee of anything, but it still improves Karen's chances of maintaining consistent appearances without getting swept under the rug. Nightwing will return to normal sooner or later, but Karen doesn't have such assurances. Even when the JSA return, we can't be certain she'll be among them.
This also increases her odds of larger media appearances. Larger media loves Nightwing even if the comics don't. Karen being an established love interest for Dick opens up more avenues for her. Early on, it's unlikely an adaption would use her over Babs or Kori, but give it some time (and probably less than you'd think) and Karen would be seen as a viable option as well. Once again, it's better chances than what she has now.
And no, of course Powerwing isn't gonna happen, this is just dumb fan stuff.
But Babs and Kori won't happen either. Babs is a solo IP and as long as she has her own book and writer, there's logistic problems with DickBabs (as we saw with Superman-Wonder Woman). Plus, DC values Babs over Dick and doesn't want to saddle her with what they consider dead weight. Babs is damn unlikely to happen. And DC has tried to minimize and downplay the importance of the NTT for Dick, which means DickKori isn't happening either. They've been very clear about that. But you know what DC loves? World's Finest pairings. Clark-Bruce. Jon-Damian. Conner-Tim. Kara-Babs once upon a time. DC might try to keep the Titans out of Nightwing, but they're quite happy to push a World's Finest combo. And Karen's a well established character, not some original creation made just for the love interest role like Shawn or Clancy. Fans dont get invested in those because we know those original characters will be forgotten by the next writer. Karen is a known IP with her own fanbase, and is less likely to get pushed aside the way a Shawn or Clancy is.
Would fans push against Powerwing? Sure. They push against everything new. Doesn't mean it wouldn't succeed (look at Grayson, we hated the idea but consider it essential reading now). And given the Babs-Kori fandom divide, offering a "neutral third option" who's more than just a throw-away original creation consolation prize isn't the worst option.
And of course, even if, somehow, this did happen that doesn't mean it would be done well. Nothing is foolproof. But that doesn't mean it *shouldn't* be done either. Karen's got nothing to lose after all, so it's not like we'd be running a risk with any of this, and if it was handled with even a half-assed amount of care and effort we'd potentially gain quite a bit.