this is about orchestration only or finding a performer of two different instruments ?
in orchestration anything can merge, a Piccolo with Tuba for instance..
in Performers, finding a person who plays Clarinet and Saxophone is more common, but Bassoon and Saxophone won't be easy to find, Bassoon has nothing to do with Saxophone, I play Saxophones and Clarinet but I have no idea how to play a bassoon and I don't own a bassoon, if you call for a single player to play Bassoon and Sax, that will be a mistake in your score.
I will name the only doubling could be used, without worries
Clarinet / Saxophones
Trombone / Euphonium
Horn / Wagner Tuba
& not so common but no problem:
Tuba / Euphonium
and of course, things like Piccolo/Flute, Oboe/Enlgish Horn, Bassoon/Contrabassoon.