If I'm Larry Scott, I would pick at least one tier I on every surface to get the mandatory status.
Clay: Berlin (Rome is too near to RG's schedule)
Grass: Upgrade Eastbourne to be a tier I
So we would have 9 main events: 4 slams (january, may, june, september), 1 YEC (november) and 4 mandatory tournaments (march, may, june, october).
2003, 2005, 2006, 2007 RG
2003, 2007 USO
2004 Olympic Gold
2006, 2007 YEC
10 Tier I, 17 Tier II, 3 Tier III, 1 Tier IV