No problem! I was glad to be helpful! I think you got an awesome roadmap for further development. I'll mention a couple things that aren't quite "lore friendly", but I've got very minor gamedev experience, and I think those things should be up to you to make for better gameplay:
I think you could easily get lost in the city designing though, as I mentioned, it's hard to design a proper soviet city for driving. I wouldn't go the traditional route on that, maybe longer stretches of road connected by intersections or something (my summer car-like Rural to city marshrutka?). I think as soon as you can overview a part of the city from one location the illusion starts falling apart, given the repetitive design of their irl counterparts and the impossibility of implementing subtle differences of various landmarks like buildings in a game. Putting down landmarks just for the sake of the player finding his way around isn't the best solution either, imo, they should be pretty humble, convenience stores, schools, hostitals, factories etc. I can't think of any well implemented soviet city for driving, but you could look into "Bright Lights of Svetlov" for design references, but it's interior focused. Another one that comes to mind is the GTA Criminal Russia mod for san andreas, while the mod itself is considered bottom of the barrel by many, I think it got a couple city design elements right, given it's major limitations.
Real Marshrutkas still, mostly, followed bus routes, which did have bus stops. It's tough to say exactly, but I think bus stops were still the major hubs for boarding passengers. More people got in on bus stops than left, But you'll have to see what works gameplay wise, I'd still leave the occasional bus stop in. The first and last stop of the route usually were bus stops and had a couple marshrutkas of the same number lined up waiting to go.
The multiple choice questions from passengers is actually a great idea, as irl passengers did often ask were an address is or where to get off. Especially hilarious situations ensued when passengers asked the driver to tell them when they had to get off for a certain place and the driver completely forgot, but idk if that's a think worth implementing early on. Another question the driver got asked by boarding passengers is if there are any sitting spots left, the answer was always yes no matter what lol.
Russian marshrutkas of that era had no documents to check, as every fare was strictly cash only, but maybe there were in other countries. Some post 200(?) marshrutkas had the ability for an electronic fare card, but that's beside the point. I think a multitasking cash taking and change giving mechanic while driving would be better suited, if you want to leave some document checking mechanism in, I think checking if a passenger is too intoxicated and refusing them the ride would be more realistic (it was a common occurence irl, but ruckus ensured either way lol). There were some rules for who had a right for a free fare (I think disabled, elderly and kids), given they show the appropriate documents, but that was never honored. The sign it the last picture I posted even mocks that fact, listing some absurdities like Tom Cruise, Nobel Prize winners and Matrix agents as having the right for a free fare. Only free fares for kids that were obviously pre-school were honored, and even that was inconsistent in the early 90s.
Anyway, I guess you can say I'm a 90s marshrutka connoisseur😂, but the 90s marshrutka experience was truly something you wouldn't be able to see anywhere nowadays given the absurdities and surrealness of it.
There aren't really many English resources (and even Russian or other eastern language ones are rare) documenting the marshurka phenomenon. But here are some I found on google that might be helpful:
https://marshrutka.net/wp-content/uploads/2019/02/Marshrutka-Stories-A-Visual-Ar...
https://mondaybazaarblog.com/2016/04/13/that-marshrutka-life/
https://travel.stackexchange.com/questions/146606/what-exactly-is-a-marshrutka-%...