You'd need pro advice on this. best advice I can give you is do it once, and do it well. get an architect and probably an engineer too to check out the place and give you possible solutions. as in for the proper removal and correction of that non-code-compliant closet. It would turn away possible tenants too. And if this is the entrance, is this one of the places you hoist furniture up and through the window? There's sometimes no easy quick fix.