would it be possible to make it so npcs interact more with the rides at the theme park
I don't know how to do that.
@Ehetyz
This mod is awesome and definitely something GTA5 needs to take away some of the artificiality of the gameworld.
One of the things that's been bugging me is the fact that peds don't really interact with the world on their own, instead it seems they get spawned in and then either walk around endlessly, stand in place, or play an idle animation like smoking.
I'm doing what I can, but sadly I'm encountering a few obstacles. For example I can't make peds walk on the sidewalk, they always walk to their destination in a straight line. This prevents me from making them walk up to stuff and interact with it (they will end up jaywalking half the time).
- Peds walking up to a soda machine and getting a drink, or walking up to a hotdog/taco stand and getting a snack
Can be done, but I need the machines' model name and a fitting animation/scenario from the game.
- Walking up to another ped and initiating conversation - at the moment it seems like they simply spawn in groups and conversations don't seem to happen organically
There's a native that does that, I'll see if it works properly. But again, i've had problems with making peds "walk up to" stuff.
- Ped spawning on a car/bike, parking it and walking away (not sure if this exists already?)
I've only coded leaving peds. I don't know how to get suitable parking spaces, so I can't task peds to park.
Also, given the ped AI, I'm afraid they will smash into everything while trying to park. Making them just leave is easier, and safer. Usually.
- Larger amounts of people entering/exiting trains/subway
I need to know how to get train/subway info first.
- More variety on the amount of people in cars - at the moment it seems like it's always one, or max 2 peds in a car and only cops/enemies occupy more seats. Would be interesting to see some peds carpooling.
Didn't think , you're right. I'll see what I can do.
- Simply walking up to a terrace/restaurant and sitting down
I've seen ambient peds walking to sofas and sitting down, so it can be done. I need to figure out how its done, though.
- Peds actually playing tennis at tennis courts, or doing other activities in places reserved for them, like golfing
Way more complex than it looks, tennis and stuff are entire gamemodes reserved for the players. Doubt I'll be able to code this.
- Peds walking up to the stationary binocular thingies and using them
If they do it ambiently I should be able to mimic it.
- Peds actually swimming in their private pools - at the moment they just sunbathe or sit by the poolside. There could even be a cycle of sunbathing, then swimming, then going back to sunbathing.
I'd need coords for these pools. 
Some other ideas for unique stuff:
- Packs of hostile feral dogs in Sandy shores/desert
This is one of the scenarios that should be awfully easy to code, so consider it done.
- Rednecks shooting up a car wreck/targets at the Sandy shores area
I really like this idea!
- Peds driving waterscooters in the rivers/rapids
Never coded water-based stuff, I'll see if its possible.
- Choppers landing/taking off from plain areas like the Grand senora desert. This could be tied to some other scenarios like drug deals.
This is on my plans already, but didn't think about linking it to drug deals.
Also if it's possible to involve the open interiors mod, seeing people interact with or move in and out of the interior areas would be pretty cool.
Yes, but I'd need the coords for these areas, or a similar way to know where to tell peds to go.

Random screenshot. I'm fixing casual carjackers , firetrucks and ambulances, an update should be up soon.
I think you guys will like what I've done with the Hunter.