But what if the key feature that lets you live out your particular character fantasy doesn't kick in until level 14? Couldn't that player claim that the game is really only a level 14-20 game? Should we just give all features at first level to accommodate those players?And also, you are selling a game with levels 1-20, so actually make a 1-20 game, not a game where you're actually the character you intended to make 3-20 and according to some design attempts just stop at 9, 10, or 12.
What is best for the game overall? Obviously, for the game to work there has to be an approachable entry point for new players. There has to be class balance. Those things are going to demand some standardization. Although there has to be flexibility so that players can develop a character that feels good to them, you can't publish a game that will be a perfect fit, all the time, for every player. Fortunately, there is absolutely nothing preventing you from taking the RAW and tweaking them however you like for your own group, as long as everyone in your group agrees.
But I'm not seeing anything in this thread that is convincing me that adding subclasses at Level 1 would be an improvement to the base game. It would definitely make the game harder to play for a lot of new players.