Is the modular aspect designed yet? By first figuring out how the furniture reconfigures, attaches, and works as a system it might then reveal the best units to work with.
As far as interesting functionality, if you nail the modular aspect that alone may be interesting enough. Consider why this system is modular, and how it differs from other modular sets.
Is it for manufacturing and smart part strategy?
Is it for consumers who move a lot and need furniture that easily breaks down?
Or is it to enable consumers to build what they need when they want?
Sounds like a fun project!