One item you seem to have overlooked, and an important one I wish to point out. When one decides to destroy much of the herbs they become rather harder to get and more expensive, this usually upsets the fighters of the land and those who need them who then turn their attentions on those causing the problem.
In the worst case scenarios if enough is destroyed it may even bring about your own city and guild feeling the pinch on herbs and poisons making one unpopular with them as well. I don't understand why one would seek to be so destructive just for the fun of it, but just remember everything has its price in the end.
Yours In Compassion,
Written by my hand on the 13th of Midsummer, in the year 1287.