Yeah, the lack of spare concerns me. I actually ended up replacing my RFTs when they wore out with regular "go flat" Michelins. Original tires lasted around 30K miles. RFTs are rougher on the uneven roads due to firm sidewall. Most trim levels on BMWs have staggered tire setup, with wider tires in the back (due to rear wheel drive car. Even in xDrive, rear wheels are still dominant drivers). Hence tire rotation is out of question! So the fronts will still wear out much quicker than rears, while camber in rears will unevenly wear the inside of the tires. It is just how it was made, to be "sporty." In prior E90 generation and new G generation, the BMW reinstated an option for a spare tire. How nice would it have been if a diesel trim were to return on newest trim cars? Eh, we just have to wait, the higher fuel prices will have folks shopping for economical cars again. If EU prices were to happen here, we'd all be driving diesels.
Anyways, having this BMW since 12/2017, I learned to appreciate a few features. For one, I find blind spot monitoring quite useful. The mirrors on BMW are bigger than Passat, greatly reducing blind spot area. However, blind spot monitoring saved me a few times. I would suggest that the car come with Driver Assistance package, which includes Head-up display, so you can see your speed without taking eyes off the road. My car didn't have too many nice features, but wife's also comes with Speed Limit Assist (a front camera monitors speed limit signs and displays the limit sign on your head up display). That way you never have to ask, what is the speed limit? Even temp speed limits, such as roadwork areas, update the speeds as camera and software recognize temporary road signs. Automatic high beams will also be useful if you drive a lot of "middle of nowehere". And definitely Parking Assistant that will come with sensors to help you avoid hitting things. My wife also has lane assist, which will warn you if you depart your lane - trains you well to use your turn signals, so car does not try to correct you when you do intend to change lanes.
I regret not waiting or special ordering the car with KAFAS camera, since that would enable speed limits, lane assist, auto high beams, etc. Retrofitting this system requires different windshield. So best thing is to order a car with everything you need, retrofitting is more costly than having it come from factory. But I needed a car urgently at a time and it was the closest one (in Dallas dealership, I believe). Local Jackson, MS dealer transported it to me with 9 miles on the odometer. Pretty nice car overall. The only issue it had was with EGR valve sticking, which was replaced under warranty. Join us on BimmerPost forums, in the 3-series section, there is a sub-section for N47/N57 diesel subforum. You will see all issues or complaints people have with diesels. And main forum for all other things. It is always good to browse these before you decide on the car. The BMW has a much more solid turbocharger than a Passat and a redesigned HPFP. Bad fuel causes HPFP to "implode" - although BMW is not immune, Bosch updated the pump with more hefty roller which is less likely to fail. But most failures of HPFP have been linked to diesel contaminated with water. Sometimes just have to wish upon a star when you refuel. My local Kroger thus far has taken good care of my dieseling needs. Good luck!