The Crimson Binome
Hero
From a theoretical perspective, there's no reason you couldn't just have a prestige class with no pre-requisites, which grants all of those necessary commonalities at first level.What I meant with "built around requirements" is that (once your prestige class is designed) every member of a prestige class have in common its requirements + the 1st level features, but also every prestige class has some requirements at least, so presumably a 5e mechanics that wants to represent the same thing as prestige classes needs to support requirements (that's one reason why I wrote that subclasses may not be good to represent prestige classes).
There's even precedence in the form of certain feats, which immediately grant the things that would have been pre-requisites under older editions. You don't need to know how to use a bow before you become an Archery Master.