The thing about homebrew class design is that, for the most part, you don't need to. As long as the overall goal is a fantasy adventure party centered around a few notable people in a team, Pathfinder does just fine in providing that. As for being in a specific, stone-age setting, mandating some archetypes and restricting equipment options is usually as far as anyone needs to go. This would need a pile of house rules, but house rules that are already out there for the tweaking.
With the myriad options for barbarians, skalds, and bloodragers, something is there for what you want. If it turns out not exactly what you want, tweaking can be done. It's your game.
But my suggestion is to start there, using what's already made, and make adjustments accordingly.
This way, you can be very specific and not give away any details you'd be uncomfortable with, and everyone here can have a more firm grasp on your goal.