Are there really lots of people looking for such a feature? A demand for npcs/bandits attacking or raiding player bases (breaking down walls etc) indeed comes up from time to time (and some people are definitely looking for such a feature), but it's hard to tell how many people in the community really want this feature 
Honestly I'm not sure if such a feature would work well in RW... unlike in other games, the building system isn't made for this... ideally the game needs a simplified building mechanic for that (where you just use modular walls, foundations, roofs etc, i.e build a base quickly with very few elements, like in most other games). With the current building system, there is a chance that such a feature would mostly result in a lot of frustration for a new player who isn't expecting this (who spend a lot of time creating a detailed building and who may not be aware of blueprints yet) 
The building system also makes it quite easy (too easy?) for players to avoid bandit attacks. A player could create obstacles bandits couldn't pass anyway (e.g. create walls consisting of countless layers of thin blocks etc), so I'm not sure if such a feature really adds much of a "challenge" to the game.
IMHO it would be more reasonable if bandits can only break through objects like doors, for example. However, the game definitely needs better pathfinding for npcs before we can implement something like that (or tinker with base raids etc in general). It's quite difficult to implement proper pathfinding in RW, mostly due to the building system (buildings could consist of so many building elements which would quickly kill performance if we take a traditional approach on pathfinding), so unfortunately it will require quite some work (definitely something for the post-storepage-update era) 
About your suggestion regarding blueprint tags specifically, basically it's not a bad idea to have tags for building elements in general, but what would prevent a player from just assigning the "interieur" tag to his entire building (and therefore preventing bandits from breaking in)? If a player can easily circumvent base raids, I'm not sure if it that feature would be really useful? 