I saw there are many good prior suggestions:
+1 water management
+? waste management [seems like a headache]
+? food management [spoilage, frigeration, etc.]
+1 seasons [and what it affects]
+1 all around combat/gear rework. [sorry, but there would be TONS of guns still around after only 15 years]
+1 more searchable locations/buildings [again, 15 years isn't enough for most buildings to decay, and depends on how close to blastzone]
I'd like to add:
Suggestion 1:
Alternative/Custom start:
Who entered the bunker with you [customizable, could be relatives, friends, strangers, etc. X max though, not much supplies]
Who exited the bunker with you [customizable, can be more or less of who entered, such as death or births]
Did they stay with MC or leave after exiting bunker [customizable]
^if stays with mc, cabin start they would stay in 'your room' with MC.
Suggestion 2:
Would like a '3rd' system, complimentary to 'Guest house' and 'Basement', that would have 'Your room' act similar.
At the very start those that join MC, will have to sleep/crowd into 'your room'
Suggestion 2 follow-up:
I don't know how many things affect happiness, but:
'basement' = various % happiness loss or gains [based on factors]
'guest house' = various % happiness loss or gains [based on factors]
'your room' = various % happiness loss or gains [based on factors]
ps. how far did MC travel away from the bunker? 15 years worth of food and water for 2 people would take up a good amount of space [not to mention the co2 scrubbers and oxygen supply, and waste management]. And I can see MC still using the bunker, for something, if he is still close enough.