Character defining traits added to CAS.

I think most people agree, especially anyone who played Sims 3, that three traits is not much and that it's not doing enough either. It did affect sims more in Sims 3 it feels, though it could partially seem that way due to them having almost twice as many traits. 

So what I propose is a separate selection of traits being added, from a different list. Character defining traits that count stronger than regular traits and affect their behaviour far more, it is the core of who they are. 

It would borrow some of Sims 2 aspirations, but without the end goals though it would affect wants and fears and Sims 4's aspirations have the end goals covered. It would allow for more drastic traits that can make it impossible to ever do some specific actions, not even when ordered and even be unable to learn specific skills. But they would get new interactions that no other sims get, and could get out of some skills some things no other sims can. Like be able to create certain items others would not think of or interact with objects in ways no other sim would consider. 

Some examples of possible character defining traits, available from teenager and up and allowed to change whenever your sim goes into a new age group: 

-Workaholic.

Their job is their identity, they never get tense from work, never crave vacation, can work extra or even from home if the job allows it. Depending on their job they might also accept calls at home from work or call to work on their own. It is easier to keep their motives positive at work, they enjoy being there. They however take getting fired way harder than other sims because to them it feels who they are is erased. They'd be going through stages of grief from it, though getting a new job can help cheer them up and whenever they are unemployed they will look for stuff to do around the house. Cleaning, repairs, etc. Not when they have a job though, then their job always comes first. They'd work on holidays if they could. They also have a hard time dealing with retirement, and prefer to not retire at all, just keep working. They can be a bit neglectful of their family and friends because work always comes first, though it can help them with promotions and getting a raise. 

-Rebel. 

These sims play by their own rules and are defiant by nature. Other sims can't influence them to do things, though if they read up on reverse psychology they can learn to use that on rebel sims. They get all kinds of unique career pop ups that are more out there, with good chances of getting fired though they could fare better as freelancers and some specific careers that work with being a rebel. They don't care what other sims think, they don't get embarrassed. Might try and get others to rebel too, they enjoy anarchy and are against conformity. They might sit on chairs or lay on couches in ways no other sim does, they might lean back on chairs (with a chance they tip over, especially if clumsy.) and get happy from telling people off.  Whenever they get fired, you get to pick one of several reponses to it for them. Some responses could actually get them unfired if it's the kind of career that can use a loose cannon.

-Apathic. 

These sims are always fine, they do not experience emotions, good or bad. They are able to deliver deadpan comedy but clearly some kinds of art and interactions reliant on emotions they can't ever do. They tend to have a blank expression on their face. They can't learn the mischief skill and react deadpan to any jokes and mischief. 

-Dramatic. 

They perform a lot of interactions in a more dramatic way, while they learn the acting skill very fast and are extra good in that profession, they are poor at anything else and very demanding. They get extra fame quirks too from a list of oddly specific ones other sims don't have access to. They change emotions fast and everything is dramatic for them, nothing is a minor event. 

-Pleasure seeker. 

The opposite of the workaholic, they just want to have fun. Pleasure before work, they actually get happy when losing a job unless there's barely any money in the house hold funds. They prefer to be unemployed and actively seek out to enjoy life and all exciting things it has to offer. They are more easily bored and their pleasure meter drops faster.

-Mundane. 

Just a boring average sim content with living a boring life away from any excitement. They don't care for anything occult or any jobs that are too exciting. They do extra well in the salaryperson career. They never do anything interesting on their own, they don't play games. They just do boring stuff and that gives them pleasure. They require little entertainment and get happy just doing every day mundane tasks. They have very basic interests and can bore others easily when talking with them, though other boring sims will be very engaged in these conversations. 

-Charlatan. 

These sims are natural born cheaters, liars and con artists. They can do all kinds of schemes like a shell game or such to hustle other sims out of their hard earned simoleans. They get special career pop ups unique to them to do it too. They get positive 'getting away with it' buffs when they avoid getting caught in their lies, and also postive buffs when successful in a scheme. These sims can't be trusted to be loyal friends, partners or even parents, though could have camraderie with other charlatans who they can discuss schemes with. 

-Knowledge seeker. 

Pretty much a return of the knowledge aspiration in Sims 2, these sims want to know all there is to find out. Science, the occult, wanting to be saved from death, survive being struck by lightning, they do it all in the pursuit of knowledge. Everything is an experiment to them, and they get unique ways to interact with occults and create things in the field of science and the occult that no other sim can, even combining the two. They might want to obtain all kinds of lab equipment and experimental stuff.