Multi-classing, dual classing, same basic thing when you're talking about trying to replicate a fictional character. that's been there from the beginning. For example, King Arthur is a human, and yet....
View attachment 429070
And they can be. What specifically did Spartacus or Sinbad or the other do that a fighter could not do?
No. Those are for inspiration, not to replicate as a statblock. RPGs are role-playing games. It's in the name. I haven't seen a single RPG where the very definition was to replicate fictional characters into a statblock. After all, how could you, mechanically? How could you have a game that perfectly replicated the abilities of Gandalf, Merlin, Kvothe, Kelsier, Aslan, Allanon, etc.? Each story and fictional account is so different that you couldn't. Each RPG picks a few of the most common tropes and tries to manage that. Nothing will ever be a perfect replication.