Simple Soffit Build to Repurpose a Closet

We are remodeling our 2001 Fleetwood mobile home, and today, we are in the master bedroom. The original closet was not deep enough for our liking so we will be framing out a new larger closet. We don't want to waste the floor space from the original closet though. Our king size bed will never fit in there but a few feet of it will. When we built our bed we did not design a head board so we will build out the closet to be the headboard. Today we want to frame up some additional walls and a soffit in the top of the old closet to give a place to install some lighting.