Add a new type of intelligence gain: Hull Classification. This should be pretty common, and would provide the hull classes of multiple known NPR hulls for the relevant NPR. This way, you can build up information on what each class is, without needing to hope for getting the full design specifications or needing to attack/board NPR ships.
I've found that despite sitting ELINT ships in range of NPR homeworlds for years, I basically only get intelligence on a handful of designs, most of which are either outdated or not deployed. An intelligence gain option like this would let me figure out which ships are tankers, freighters, etc, in a much more practical time-span