Of course, warring nations take each others S&D all the time. you know, in world war two, all the americans just took platoons of fat cat bankers and told them to buy all the beer and bratwurst. Real talk. Totally serious.
Frankly, in the next strat, you should be able to set who is allowed to trade or interact with your fiefs by group. its just stupid that this idea is even able to be implemented.
Why?
In WW2 if I remember correctly all sides carpet bombed the shit out of manufacturing. This is same same but different. You are effecting production, you are attacking production. The fief manager can boot you out of a village, if they aren't vigilant enough or undermaned why not take advantage of that and rape them out of their economy???
Oh that's right, you totally should because it's a good idea.
[youtube]https://www.youtube.com/watch?v=VufilzHKTqk[/youtube]