In that phrase, there's no need to pluralize "one." It makes perfect sense replacing "we" (first person plural) with one (third person singular), just take out the "all"
"One must feel excitement and strangeness ..."
You could make it "they" or "people" (third person plural), as well.
"People must feel excitement and strangeness ..."
Ones is the plural of one, but it can get a little awkward. Read a sentence aloud to yourself. You can usually tell what sounds "right."