For sure, there was and is lots of potential for flavourful neutral cards in both games. In Conquest, for example, there was no particular reason save gameplay balance that cards like Ammo Depot, Calculated Strike, Holding Cell or Homing Beacon to not be neutral, and logically in Caius Wroth could be neutral, so too could be an Interrogator Acolyte.
In Five Rings, there's lots of potential for neutral concepts that cross court boundaries as well: concepts of seppuku, obedience to the Daimyo, hospitality, tea ceremonies, calligraphy - all these things are universal.
But I agree with Atrus - the fewer neutral cards we see, the happier I'll be. On the one hand there's a sense of value in a card that you can use in many decks, but for me personally, that's greatly outweighed by the annoyance of not being able to have more than a couple of game-ready decks without moving cards from one to the other.
Another annoyance here is the Provinces, of course, which also are going to overlap a lot, a bit like Plot Cards in AGOT often being needed for more than one deck.
Hoping that like in AGOT plot cards, the number of options for Provinces will increase rapidly, decreasing the need for overlap.