As an alternative to implementing the light fixture as pp2, or as a smart parented figure, you could inject the actors for the light fixture into the house figure (assuming the house is a figure). Actor injection would seem to have some advantages in this situation, as it is not subject to the hanging problems associated with smart parented figures, or the name incermentation associated with props.

Not many people realize that you can inject new actors into an existing figure, but it's quite simple, though there are some limitations.

The limitations stem from the fact that the file to inject the new ators can't contain a 'figure' section. The main limitations are:

1). Actor injecion can't add welds, so the new actors won't be welded when they load.

2). If the new actors are to use materials that are not defined in the target figure, then you will have to put them in the individual actors and use 'customMaterial 32' to tell Poser to look for them there. This will have consequences for how they are accessed in the Materials Room.

3).  Actor injection can't add IK chains.

All the above things could be fixed by the later application of a pose, but that's adding another step.

One last limitation. 

5). Sometimes (eg when injecting body handles) it is desirable to place new joint paramiter channels in the target figure, actor injecion can't do that (perhaps it could call a py script to add the channels).

If you are interested in trying actor injection, I will post details of how to do it.