I think that some sort of stat points would be cool to improve power, spin, accuracy, etc. Maybe for every 10 "PERFECT" swings you could get one stat point and add it to the ability you want to improve with a max of 10000 so as to make for a very indepth game and much harder and more interesting courses down the road.
Also, I wouldn't mind more customization options for my golf avatar, but I know it will all come in time. NEW CLUBS ARE A MUST!!! 2-3 new sets per tier minimum. All courses need to have Front and Back 9 so you can play the full 18.
A way for players to possibly gamble with eachother. Maybe you would earn it through a fake money system, where birdies are worth $5, Eagles $50, and Hole in Ones $100-5000 depending on distance. This money could also be used to purchase new clubs, and other gear (i.e. shoes, shirts, pants/shorts, hats, glasses, etc.) So a Golf shop would be needed in the menu.
Well, Those are a few suggestions I had, which if the programmers aren't too busy working out bugs, I'm sure they've already been working on, If not PLEASE START WITH THE CLUBS AND NEW COURSES!!!!