There is a curious trend now of rock groups partially reuniting with new, also famous, singers. Examples include:
Ray Manzarek and Robbie Krieger of the Doors with Ian Astbury
Brian May and Roger Taylor of Queen with Paul Rodgers
Elliot Easton and Greg Hawkes of the Cars with Todd Rundgren
Leaving aside the question of how bad this trend is, are there any bands you’d like to see reunite with a different singer?
Well, they had to get someone with a weird, oblong-shaped head to replace Ric Ocasek…
I don’t think the trend is all that new, it’s just that the observers get younger each year. 
Anyway, there’s an obvious answer.
Take the group who lost a drummer and bass player and merge them with the group that only has left a drummer and bass player.
That’s The Who and The Beatles. As I said in another thread, you could call them Who Beats Who.
There was a thread recently about Alice in Chains reuniting with a different singer. (That’s just as another example, not a band I’d like to see.)
Alvin from the Chipmunks? Yeah, that I’d like to see.
Alvin in Chains…yeah, I’d pay to see that too.
I’d prefer The Whotles, myself.
I’m actually listening right now to the Alice in Chains reunion show, with Phil Anselmo of Pantera singing “Them Bones.”
It’s interesting. I still think the best choice for a new AiC frontman is one Maynard James Keenan.
Pink Floyd recently semi-reunited for a benefit/awareness concert. I’d pay some serious cash to see their full line-up reunited. (Okay, who am I kidding, I’d pay something serious just to see 70’s Floyd on tour.)
Do you have any examples? The obvious one is Sammy Hagar and Van Halen, but that was just a change of singer, not a semi-reunion.
Not sure what you mean by this, since it was the full lineup that reunited, if only for a few songs. If you mean you’d like to see the original lineup, with Syd Barrett, reunited…well, how about getting Robyn Hitchcock to take his place?
I was trying to think of people to take Syd’s place, to make my post more relevant to the thread, but just couldn’t think of any. Robyn Hitchcock wouldn’t be bad, now that you mention it. Nor would the lead singers of Echo and the Bunnymen or Jesus and Mary Chain. (Also, a lot of the Cure sounds Barrett-ish, but Robert Smith’s voice sure doesn’t.)
CSNY. CCR. Skynrd. Allmans. Does Tears For Fears count? I know they had a lot of different guys besides the two lead guys, but maybe that was the case all along (sort of a two-guys-and-whatever-session-players-they-find approach). Starship et al.
It’s older than that if you count the “New Platters” and “New Drifters” who started out with one or two of the originals and are now probably still creaking along in multiple incarnations with some six-degrees-of-separation link to the original.
Doesn’t quite fit the OP’s criteria… they broke up and reformed twice, but never with a different singer.
The remains of Styx teamed up with Canadian singer/keyboardist Larry Gowan, who has taken the place of the departed Dennis De Young since 1998 or so. He sings their best-known songs, they play his. (I’d love to hear them do “A Criminal Mind”…)
Yeah, maybe I should read the OP, which also disqualifies Starship and Tears for Fears.
Oh, notoriously and recently, INXS.
Which brings up the point, why is this happening?
More media outlets. More need for gimmicks. “Hollywood out of ideas” – marketers have gotten hooked on regurgitating popular concepts. Boomer-led navel-gazing obession with everything about the Boomers’ past (we’re obviously past the main cohort of Boomers being culturally dominant on the popular music scene, but the succeeding generation took from the Boomers the masturbatory tendency to wallow in its own fabulousness and its past fripperies).
And . . .