1. Grass
2. Shutdown/Teardown the hotel (or some of the hotel), remove all the outfield seats except for the 100/200 levels, and install retracting glass walls/windows to make it less cavernous (like Miller Park https://en.wikipedia.org/wiki/Miller_Park_(Milwaukee)#/media/File:MillerPark2.jpg or Marlins Park)
3. Tear out some walls and make the concourses open air in the 500s (not sure if possible)
4. More bathrooms or larger bathrooms
5. Better food options