Herbalism should extent to plants that aren't weed. The fact that it's such a single-minded skill which is used solely for crime is outrageous when there is a surplus of different plants (with gmod models) in the world.
You ought to be able to grow other plants such as watermelons, oranges, bananas et cetera. If they were given a bonus over the store bought ones (such as a speed boost or increased healing), they'd be more readily bought by players and grown by players. There would then be fruit shops cropping up in the city too, promoting passive RP (if the player wanted to sell to others, or he could sell to the NPC for less).
But that's my opinion.