Hi! I tried the game out until I completed 8 orders. Here's my feedback on it:
1) I feel like maybe after the first 3 orders the game starts to get boring and repetitive a bit. Some of the customers are repeating too (I had 3 instances of the person who wants lavenders for their wife).
2) I did feel a bit relaxed while playing, yeah.
3) Yes I definitely think some sort of progression would work well with this game. I think a day to day thing would be cool to see, every day having 5-10 different people/scenarios. And as you said above, a ranking up system could work along with that.
4) Since different people request different flowers, it'd be nice to see the different flower icons next to the three actions you already have. Then you can click or drag the flower to make it appear on the soil. That way there's more interactivity. I'd also like to see a more visually appealing background or have some music/sound effects for the actions. Anyway these are just my suggestions, I hope you enjoy making the game however you'd like to :)