Currently, plugins are not without a cost, as they impact startup time and memory footprint, as well as potentially expanding the Add Object and Plugin Tool lists.
I don't see NWC offering a facility to encourage installing everything. However, the community could create a *.nwc master file of objects that demonstrates a large collection of them. This master file would enable something similar to what you describe, as it could be used to quickly download and install a large collection of plugins, and also demo their capabilities.
Alternately, perhaps an overview page that demonstrates many of the objects would be helpful.
I'll think about it. This Plugin board is meant to provide much of this now, as it can be casually browsed.
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