I like a lot of the ideas people have on this thread. I haven't played The Sims in years, but just got TS4 about a month or so ago.
My boyfriend asked earlier if his Sim hates mowing the lawn as much as he does. I told him there isn't mowing in the game. So yeah, yard work could be an interesting idea. Not necessarily a dude thing, but dudes seem to get stuck with it often. Even if the grass doesn't visually grow, but some kind of other indication that your lawn needs mowing. Maybe even fines if your lawn hasn't been mowed in a while. Similar to the laundry system, it would be nice if it is only in play if you have a mower so you don't have to mess with it if you don't want to. It could also be a chore or job for kids, I suppose?
Let me torture my boyfriend's Sim by making him mow the lawn!
And of course, seeing a band/ musician system of some kind would be awesome, but I know I've seen people wanting that though. The bf is a working musician and his work is much more like gig work than the Entertainer career. Taking performance and recording gigs, doing rehearsals, etc. That would be cool. I don't know if any of this would be super complicated. Right now I guess I'll just giggle every time I see his Sim leave for work in a tux. Again, not necessarily a guy thing, but at least in our area, there are a lot more male musicians than female. You always have chick singers sure, but actual female musicians? I would say I know 10 for every 100 males so I'm calling it a dude thing. Lol