I've seen a lot of discussions about this but I think the points you make are interesting. (Sorry for the incoming classic Snowbnuuy text-wall...)
I think Lifestyles and Sentiments are something the game needed to spice up relationships with others, individuality, and such, even if some of the Sentiments are a bit off at times (Once my sim got a call from another asking if he thought a hotdog was a sandwich, he said no, and then the calling Sim had a Festering Grudge or something like that. A bit much : P ) The interactions are a bit more meaningful when there's some kind of (sort of)-lasting impression from certain interactions. Hopefully soon we may get more Likes/Dislikes and Sentiments I hope. I also agree with grieving being very watered-down. I'm hoping one day we'll get some kind of funeral event we can do in TS4, to add a little depth to loss. I think the moodlet should be extended a bit longer than just two days.
The Reputation feature that came with Get Famous comes to mind, but I still feel like there's not a massive consequence to negative reputation. My one Sim that had an Atrocious reputation just got negative reactions in public now and again, but could just bribe their way into friendships and such, so it's easy to still get what you want despite the apparent 'drawback'.
Back when I played TS2 especially, I feel like there was a lot more room for interesting conflicts, especially when it came to TS2 pre-mades and all the existing family dramas and inner conflicts within families. It felt fleshed-out and it was fun to play out the stories in different ways. And of course you had the chance cards for jobs and such that could get you fired, and so there was chance for a spanner to get thrown in the works. I know TS4 has some similar career chance cards, but for me it ruins it a bit that the outcome of your decision is written on the bottom of each choice; I like the surprise element personally. I got around it by flipping a coin and choosing accordingly what the outcome was.
TS3, I feel there was more consequence for screwing up your romantic relationships with other sims. First thing that comes to mind is the old Romantic Reputation feature. If you cheated and were unfaithful, it would negatively affect your reputation and would often make it harder to find a new partner later on down the line. but now there's none of that risk and cheating on your spouse or whatever doesn't seem to have as much of an impact on the rest of your Sim's life. This is actually a feature I want back since the romantic department in TS4 is lacking a lot IMO.
I like your idea of Random Events. Maybe there could be an on/off toggle in Options for it, but I think it'd be a good idea to have some variety of things that can really throw a curveball.