I have one project in progress where this would have an incredible impact: a stadium with 10.000+ seats. I already optimized this partly by grouping seats and running them through Blender to merge groups and then repeat the same for rows. Imagine the impact of defining a single seat and 10.000+ positions instead of 10.000+ seats! The project would shrink from 300+ MB to just a few MB's [:))]

Yes.
SH3D should have to make this kind of furniture library storage and loading so it shouldn't be hard to do. But it would be great for the ecology of the creation.
Including making a lamp with multiple light sources, I'd do it too. But the process is so cumbersome that it can be very painful and agonizing.
If we can build the underlying infrastructure well, then we can have more and better furniture!