New herbs are steadily being added to the game, but I had a few ideas about how to perhaps make the experience of growing and utilizing them more enjoyable. Firstly, some new herbs with culinary (as well as medical or therapeutic) applications -- mint, rosemary, sage, and others -- would be a welcome addition.
How about herbs as non-essential ingredients to increase food and drink quality? Use spices while cooking to amp up the FEPs. Chives or parsley could be applied to a prepared meal as a garnish to improve its effects.
The process of emptying a garden pot every time an herb is harvested is a bit unrealistic and tedious, too. A new sprout of the herb stays in the pot after harvesting, and its new quality is a function of the quality difference between the soil and the plant, with soil quality decreasing and herb quality increasing at a 3 to 1 ratio. This would make it beneficial to change the soil when its quality becomes depleted, but not essential. You'd still have to water the pot, of course.