Boolprop!

I also suggest starting an Apoca-BaCC with multiple households, otherwise, this would be an adult starter apocalypse, which is superhard in its own right already...

Looking at the apocalypse rules, if we compare it against the original BaCC, there are three rules that make combining these two almost impossible:

Hopelessness = Can't move in
Military = Can't move out
Business = Can't buy/open business (since you need a level 10 business by the original rules to open a business career, this would be completely impossible...)

Now the hopelessness and military thing could actually be overcome with several households, if they all have at least a few females there... yeah, this is probably really discriminating, but that way, it might be a nice challenge to keep a household from dying out in the beginning - as for star gazing, even if we lift the music restriction from the apocalypse, chances for alien babies are small for males probably starving and freezing outside...

If we start with at least 4 households, we could also place an army base, and with military open, actually overcome the above obstacles of hopelessness and military....

Criminal could be considered a good starter career to be lifted too... and maybe Adventurer, as in seeking adventure in the apocalypse instead of robbing people...

law enforcement might be only lifted, if military is lifted already, as it should deal rather with civil unrest than zombies... and I know, resident evil thinks otherwise...

Science is possible too, maxed logic if you spent your time playing chess is feasible at least.

Medical on the other hand, which requires 1000 population by the original BaCC , seems a bit too late... perhaps at least 3-5 sick people would already be enough here..

Culinary with its level 5 restaurant by the original BaCC would again be impossible with the Business restriction, but maxed cooking skill could work too, however everyone taking culinary should have it maxed until alevel 5 restaurant opens.

The Business restriction finally could be opened by founding enough new households to place enough unowned commnity lots ~ 5 lots = 20 households?

all the other restrictions could to a certain degree be locked until these have been opened - you can be a great musician, but without an agent selling your cards you can't really top this... easiest way for locking would probably be a population restriction (100 Population, 250 Population, 500 Population, 1000 Population, 5000 Population...)

To avoid overuse of Business Districts and Unis later, I'd actually use my old idea, that you these counts towards the population only once (3 unis = still only Sm +5), while certain requirements (e.g so and so many in a career) lifted will eventually get you specific landmarks/buildings, that add 5 to the Sim-multiplicator , so if we'd get 40+ together, that allows an SM high enough to get 50000 population.

Some ideas for those:

Gamer: Video Game Development Studio | Convention Center
Law: Law Firm | Courthouse
Journalism: Magazine / Newspaper Publisher Headquarters
Education: Elementary / High School
Adventurer: Embassy Office
Music: Record Store | Music Store | Coffee Shop | Summer Camp
Recording Studio | Concert Hall
Artist: Art Supplies Store
Roadside Attraction & Gift Shop (“Lucille, Largest Llama in the World”)
Comic Publisher Headquarters | Photography Studio | Art Gallery
Natural Scientist: Laboratory (Animals)
Show Business: Film Studio | Broadway / Theatre
Paranormal: Tarot Reading Shop
Entertainment: Pub (Open Mic Night) | Lounge
Dance: Dance Studio | Ballroom
Oceanography: Aquarium (Dolphin Tank)
Intelligence: Detective Office | SCIA Headquarters
Architecture: Construction Site | Architecture Firm
Athletic: Sport Stadium / Field
Business: Corporation Headquarters | Franchise Office
Criminal: Dog Track / Horse Racetrack | Bank
Abandoned Warehouse | Docks / Airport (Smuggling)
Culinary: Restaurant | Fast Food
Slacker: Golf Course | Gas Station | Convenience Store
Record Store | Movie Theater (Projectionist)
Politics: Campaign Office | City Hall
Capitol Building
Science: Research Lab | Technology Lab (Inventor)
Mad Scientist Lab
Law Enforcement: Police Academy | Police Station
Military: Military Base | Air Force Base
Space Science Headquarters (Astronaut)
Medicine: Hospital | Research Clinic

just a few scribbles for now...

I don't just want to blend the rules of both challenges either, but it's a good start to see what goes and what doesn't from the classics...

So perhaps in an Apo BaCC, careers restrict stuff like an apocalypse, but taking the careers is restricted too, as the infrastructure for jobs and of course the city is destroyed...

Thinking about a 3-part system:

1.) requirements for taking a career - like in the classical BaCC, these are population numbers, community lots (stadium, army base etc..), events (fires, burglaries), skills (max logic/charisma)
- if these occur, a single or limited number of sims can take a career, if it shows up in the newspaper (still restricted to only the first career being available like with journalism and science?)

2.) lifting restrictions: To make this more a teamwork thing for a BaCC, restrictions dictated by this career are only lifted if:
- a Sim tops the career AND
- several Sims also enter the career AND their job levels added together are equal or bigger than a certain number ~ for example 50, so you need a level 10 topper, 5 level 7 and 1 level 5...

[Note: the idea, that only the household profits permanently, where a Sim has topped a career, while the others need to top it as well and it's only suspended till that Sim drops out or dies, is good too, but I still remember the uproar about Pinstars criminal/pet career suspension rule and how difficult it was to keep track... admittedly, keeping track of the number of Career levels added together sounds difficult too....]

EDIT: Another Idea: a topped career is not absolutely necessary, but provide an extra bonus (+5 job openings?)... makes it not necessary to top it, but you still end up with several people topping the career to get the numbers together

3.) restriction for City - again, to get rid of the BaCC's need to place an insane amount of Business districts and universities, I propose Landmarks counting towards the SM, while Districts and Unis only count one time... landmarks can already be the above community lots that restrict taking a career.

EDIT EDIT: Another idea for the move in/move out problems from above - since you wouldn't need to be blood related to a founder anymore for the teamwork lift, adoption of apocalypse orphans could help a single male household to survive... and also overcomes the problem that most challenges make adoption unnecessary or unwanted... poor orphans...

Sifting through the apocalypse rules, I went for another 'change as little as possible' approach - here's what I came up with so far:

Base rules:
- Everyone playable can lift restrictions.
- One topped career is not enough/required; you need to add the levels of all playable Sims in one career in the hood together; if it is higher than 100 (hopelessness 50), the career restrictions are lifted
- A Sim can only contribute up to 10 level points for lifting a career when he topped it; teen/elder careers count as level 1-3 of the adult career.
- Several contributions to different careers by the same Sim are possible.
- A townie/NPC moved in with a job doesn't count with that job; they need to quit immediately and only their new job counts

- Hopelessness: you can't have more than 4 households in the hood.
- Even with Hopelessness in place, you can adopt; Social workers are desperate to give apocalypse orphans a home, but nobody else wants to take them.

- Music: only after lifting music, a Household with a rock god cam surpress the artist restriction for said household

- Military: You can visit community lots, if you use a car.

- Culinary: you can prepare food on a grill on community lots once per day, not on the first day if you already ate at home.

- Adventure: Tents and hotels are restricted

BaCC related Rules:
- CAS-Points: You Start with 10 CAS Points; if a CAS-Sim dies, you don't get the CAS Point back
- Earning CAS-Points: If a household dies out or consists only of an uncontrollable Elder, you earn a CAS Point = even with all Sims dead, you can always add one more household.