I've solved this problem by trial and error. See below for my solution, it's a bit lengthy but it works on my MacBook Air (2014).
1. Download and install the latest wineskin winery app:
http://wineskin.urgesoftware.com/tik...page=Downloads
2. Run the Wineskin Winery App
3. Click that + button to add a new Engine
4. Choose WS9Wine2.6 and then click Download and Install
5. On the main window of the Winery app, click "Update" button to update wrapper version
6. You should see the wrapper version is Wineskin-2.6.2 after the update
7. Create a new Blank Wrapper
8. Choose whatever name you like for the app and create it, the default name is MyCoolWrapper
9. Right click the app you just created, choose "show package content"
10. Select and copy that Wineskin (this is version 2.6.2)
11. Go back to the Project 1999 wrapper, and right click it to "show package content".
12. Paste the Wineskin and replace the one inside the Project 1999 wrapper.
13. Run the new Wineskin in the Project 1999 wrapper (you may see some error message, please ignore it)
14. Choose advanced -> tools -> update Wrapper
15. quit the app
16. Follow step 1 of Riddick's original instruction.
17. Launch Project 1999 wrapper, and the game should be running!