David Brownlee wrote :
| 	How about 'subcategories' - it would still involve an additional
| 	step to generate the 'SEE_ALSO' lists.

I would be happy with that.
But as every 'centralized' descriptions, people would have to be aware of
existing 'sub-categories' to be able to choose one that would be adapted
to their (new) package (and not create a new one).

Don't know... I'm not a pkgsrc guru :)