Consider two of the iconic rock groups of the 1960s “British Invasion“: The Beatles and The Who. For the purposes of this thought experiment, let it be stipulated that all members of both groups contributed vocals, to some extent, to their respective groups.
Both bands had four members during that era. Each band has had two of its foundational members die in the intervening years: The Beatles have lost John Lennon (guitar) and George Harrison (guitar), while The Who lost Keith Moon (drums) and John Entwistle (bass).
Meanwhile, each band has two surviving core members: The Beatles’ surviving core members are Ringo Starr (drums) and Paul McCartney (bass), while The Who’s surviving core members are Pete Townshend (guitar) and Roger Daltrey (primarily vocals, though he’s also a guitarist). Frankly, with a guitarist like Pete Townshend, do you really need a second guitarist, other than for specific songs? Besides, when bands tour these days, they often have musicians besides the core group. Let Roger sing; if a song needs extra guitarists, they’ll be on hand, never fear.
Finally, Pete Townshend was the primary songwriter for The Who. Meanwhile, Paul McCartney, though his songwriting with The Beatles was generally in collaboration with John Lennon, has had quite a successful solo career as a songwriter.
Ladies and gentlemen (and those who identify with The Athlete Formerly Known as Bruce Jenner), I suggest that a new band be formed, at least for one tour together: The Whotles!