Currently I am limited to a smaller hatchback (Honda Fit) so a more intense shelter like a wall tent, yurt, or hexayurt is off the table for now.
the core shelter:

A Seek Outside 6 man tipi. An 8 would be better for this but the 6 is small enough to manpack in a pinch. I currently have two poles, one carbon fiber and one beefy aluminum, I have a mix of army surplus and recreational stakes, but I should buy some more of the surplus ones as they have proven their worth when weight isn't a concern.

A hammock and straps for some camp furniture, a Seek Outside two person nest for bug and ground protection, and a recently added tomahawk for stake pounding duties. I may swap this out for a larger hatchet/hawk or simply a dedicated hammer.

A bit redundant, but in the white dry bag is a second tipi in case of tent failure or in case I can't find enough open ground to pitch the 6 man. Still large enough for me and the wife, but less comfortable. With my two poles I could also setup this as a guest house, but I should throw in some more stakes to make that practical. Next to that is a Kelty Noah's tarp 12' for awning/porch use. In the ziplock baggy is a string of LED "fairly lights" from eBay that plugs into any USB power source for soft tent lighting, and a Black Diamond AA lantern for brighter task lighting. The orange things are large inflatable REI InCamp mats that clipped together make an almost queen sized bed and some ground insulation. Bonus picture of smaller tipi:


The only reason I don't include bedding in this is it maxes out my North Face Basecamp duffle that it all fits in so nicely. For trips or emergency use we'd either add our sleeping bags from our BOBs or more tradition bedding from our house.
In use a few weekends ago:


This was the first use of the awning in this setup, and because I didn't know you weren't allowed to guy out to trees at this campground I had to wing it with the poles; the third pole was recruited from my INCH bag I'd taken on a whim. Despite how large our tent is, getting stuck in it during storms is still a drag, and I now consider an awning tarp a must have for both morale and productivity.

My water system was crude but useful, for a longer trip or an emergency I'd throw in another MWC.

Since my SOP is more or less to at least get out of site of the car before setting up camp I'm experimenting with pack frames to make fewer trips. Here you can see my camp kitchen, some food, and our cooler strapped to a MOLLE II frame for easy packing. I think two or three of these could carry a pretty self sufficient medium term camp; Perhaps one for kitchen and food, one for shelter and bedding, and one for water etc.
It had been a long time since I'd car camped (for a long time we slept in the back of our car more often then setting up a tent) so I was a bit rusty. Things I'd like to add to round this out:
1) more guyline. I had enough for this trip, but more would have been needed to weather a storm.
2) more poles. In case I can't use trees again for whatever reason, I'd like at least two more dedicated tarp poles for a covered living area.
3) more robust water system. A big filter that plays nice with the MWCs and perhaps a tripod for gravity filtering and gravity feeding water could be handy.
4) A larger cooler. I debate a large cooler's usefulness in a BO situation, but perhaps being able to take some of the fridge and freezer with you on the way out could be good. Likely the cooler would be left with the car and not packed to camp like the rest of the food and cook gear. For car camping the utility is obvious.
5) A sacrificial tarp. Since I am used to backpacking (taking down your tent every morning) I forget how much UV your shelter can soak up if you are stationary for a few days or longer. I'd like my tipi to last for many years yet, so especially in sunny Colorado at high elevation a cheap, consumable tarp could save me a lot of money in the long run.
6) more stakes. I had only 2-3 spares with this setup, and certainly couldn't pitch both tents and an awning. I would have need more if I was going to pitch the tipi for a real storm.
Lots of other stuff I could add, but more intense tools, power infrastructure, security, and food topics I think are better left for separate threads.