Opened doors take up space, so go for roller blinds if you really can't spare the floor space.
Design: 19sixtyseven
No space to display your knick knacks and mementos? Give some of your doors mini shelves like these.
Design: Country Concept
Pull-out counters give you extra prep space if you need it, and can replace the need for a breakfast counter.
Design: Dan's Workshop
Small spaces can't afford to feel cluttered. A dresser you can tuck away is one solution for the bedroom.
Design: Metaphor Studio
Turning the bomb shelter into a store room is a common idea. This shouldn't stop you from using the space infront of it, though. If the layout is right, you can turn that space into a dining area -- and a dining table with wheels allow you to access the bomb shelter easily!
Design: Three-D Conceptwerke