I began thinking this through when I was reading the excellent "Early Years" biography, and the author speculated that there could have been a lock-up on an industrial estate labelled "J.Deacon, Electronics" if history had chosen a different path for the members of Queen. So, here is what I feel the members of Queen may have ended-up doing if fame had not called and music had slowly become a fading memory of youth:
Freddie: interior designer. He would have eventually tired of the limitations of graphic design, but would perhaps not have been talented enough to become a widely exhibited fine artist. Instead, he moves into interior design and achieves minor celebrity on a house makeover show.
Roger: initially a lab technician, he slowly moves up the ranks of a pharmaceuticals company until he is the regional manager. Gets fired for sexual harrasment after nobbing one too many secretaries.
Brian: physics teacher. The kids make fun of his clogs. He quite fancies that bird that used to be in Eastenders. Turns an old fireplace into a nice sideboard on which to display his bowling trophies.
John: surveillance operative for MI6. His ability to blend into the background earns him a distinguished career in the world of covert ops. Slips up just a little when he tells Tony Blair that Iraq definitely has WMDs.
Spike Edney: bricky.
My guess:
Freddie, sticks around, finds another band, carries them to success, goes on his own, has an Elton John, Billy Joel like solo career.
John Deacon finds a spot somewhere, being a songwriter for a band that is so, so. They fade away, and he has a career of obscurity.
Roger Taylor eventually gets pulled into a great band, but is just the drummer for somebody, eventually getting some kind of solo work done.
Brian becomes the great tragedy, going to the top in the Astronomy game, abandoning music professionally, depriving the world of his musical greatness, but adding strong work in science.
Thank goodness we will never know.