I would like some way to influence how each of my sims skill up, perhaps through their traits or CAS, or even choices they make in-game. Perhaps give them strengths and weaknesses? For instance, a non-creative sim should have a harder time leveling up in skills that require creativity like painting, regardless of the moodlets they happen to have at the time. Maybe limit it to the point that they may never even achieve the maximum level for painting. Another example, if I have a non-foodie sim making blt and grilled cheese sandwiches every day of his/her life, this sim shouldn't level up in cooking the same way as a foodie sim, who maybe tries out more complex recipes each day. Maybe not everyone will like something like this, but I think this would make each sim more unique, and their traits may even have more impact on how they develop.
The way money is handled in the game could be improved upon. Some kind of banking system, so that sims can have the option to combine incomes or choose to keep them separate. This would really come in handy when splitting households. Also, I'd like my sims to have to pay for their clothes, shoes, jewelry, etc. They should also have to buy their groceries, etc. If they run out of this, they shouldn't be able to cook.
I'd also like to see stronger consequences and more appropriate reactions in game. I always find certain reactions so disappointing. Mourning a death is more strongly influenced by physically witnessing the death, regardless of whether or not the sims had any relationship at all. My sims have a stronger reaction to a thunder storm than seeing their loved ones abducted by aliens or attacked by vampires. These events should have more of an impact and shouldn't be forgotten and dismissed so easily.
