should i add built-in closet

[Bob Mane]

so I have a 1200 SQ FT open concept chalet style (timber frame from timer onsite, white stucco very nice). 

It is 600 up and 600 down in walk-out basement. full bath on each floor 

Problem is it has listed as once bedroom becasue only closet is downstairs. 

Upstairs has sort of vaulted area in "living room". 

Idea is to install full wall built-ins like 8' tall by 10' wide in order to get it to appriase as 2 bedroom.

will it work?