I found it doesn't work well with party. It works great solo though. The problem I found was with out the more feature rich class features you needed to focus more character. In solo you can really do that well in larger party divided attention makes that limited per player and player get bored really quick.
In a group very into role-play sure it could be fun for a time. If your group is committed to this idea, ask them to make normal non-NPC characters with a lower point buy and to distribute their skill points in a more "practical" way. They have PC classes, but they also have jobs in town. The warrior type is a town guard, the spellcaster is a scribe, etc. Explain that they are not seasoned, grave-robbing, murderous adventurers... yet. Power Attack is solid choice as a first level frontliner, but Alertness or Improved Initiative would better serve a town guard. Color spray is a good spell, but a scribe would probably opt for comprehend languages. A skill point in a Profession or Craft skill would be a must, unless the character is a drifter or unskilled laborer.
Hey, so I actually was playing with a very similar idea before. My plan was to do the same with the NPC classes but after a major event (read: families are killed by orcs in a raid)they set off on a small adventure, low CR like you said, and then level up to their first "Hero" level. Thus locking them into that career track. I think yours sounds very similar just obviously without real classes coming in.
To that, my biggest issue I had was BALANCE. NPC classes don't work well here, which don't get me wrong I like rolling for stats vs point buy so balance is not my main point. However, it does suck to be a commoner. Literally nothing is in your favor. So unless that player is cool with being the worst of the worst then it's probably not going to be picked.
My biggest tip is that while it's a good idea and I think keeping PC levels in but at a Slow Advancement XP track and having the level CAP be like 10 or 12 is a better approach. I went as far as even making some house rules that limited character progression to keep them "weak".
In the end if the players are cool with it and you like it who cares how it works as long as it works.
I dont get it well, you say boring cause all levels are kind of the same thing?
Not really the same but limited in scope. For example the aristocrat will be socializing with the nobility but he warrior will want to bashing heads. So you make the warrior the body guard, well nothing happens to require a body guard in most cases. So bored warrior.
This happens with normal classes too but those classes usually have enough features to useful in those situations. The fighter is the exception, they suffer the same as the warrior.
Now in solo, you can focus better on the scheming nobility with the aristocrat or send the warrior out as armed patrol with city watch. With normal class the whole party go out on armed patrol. An aristocrat would not.
It's not that it's impossible to do. It's just more tricky. It's hard enough to do with normal classes using NPC classes just makes it harder.
This works well for lvl 1, then the players get to go into other classes.
For a entire game? Well, aristo has possibilities if it's not a combat heavy game.
Played a level 1 commoner one shot where the players were all farmers once. For some reason the group liked it so much they wanted a sequel. And then another... eventually got a bit absurd.
Back in the D&D 3.5 days there was a post on the old Wizard's Message Boards that was just the written story of a Commoner in a Solo Game. So a NPC class game CAN be done. But you need the right player(s). Most of the players I have meet would not like the idea of being an Average Joe. Which IS perfectly reasonable considering that part of the fun of these games IS the power fantasy.
http://www.zioth.com/roleplay/campaign/joewood/index