I talked to my favorite builder a while ago about this luminaire vs blank cover issue and she said the policy at her company is that there will be a switched receptacle available if they are leaving a blanked off ceiling box. I know the IAEI chapter here is split on the issue but the majority says a blank cover is an "outlet". I dissagree because an unqualified person can't get a light in that room. If they used a cover with a receptacle in it I would agree it was an outlet. You could "swag" a light in.
I still think the luminaire manufacturers are missing the boat by not making a pluggable socket/hanger that would accept an industry standard luminaire or fan. If swapping luminaires were easier, people would buy more.
I have dabbled with a couple designs that could carry heavy fixtures on snap in studs and incorporate a NEMA 5-15r as the electrical connection.
This would fit in a regular ceiling box.
I also dabbled with one using a duplex 5-15 for fan/light combos.
