Trying to visualize a simple and light bed structure that can morph into a table and benches for day use. Simple boxes underneath for storage.
Convert to bed. Drop table down into footwell and spread out cushions into a mattress.
And there is also this interesting arrangement which makes a long sofa.
What I like about this design:
Satisfies the need for multi-use components.
Minimal use of wood. Probably less than one sheet. So it is light and simple to make.
Provides some fixed storage underneath, which can probably be used to store bedding.