A global organization's network is destroyed and you alone are in charge of redesigning it: What IP addressing scheme would you go with?

Let's say in this context that you work for a huge organization with multiple data centers and over 300 remote sites. In this case, you cannot follow the cutesy "'10.<site>.<vlan>.<host>" model; you have to be more efficient. How would you go about it? Would you allocate the primary blocks of IP addresses geographically or by subnet role (ex: voice, data, server, management)?

I'm thinking I would probably allocate a 10.0.0.0/11 subnet to each region (10.0.0.0/11 to North America, 10.32.0.0/11 to South America, 10.64.0.0/11 for EMEA, 10.92.0.0/11 for APAC) and then hand out the remaining IP addressing space to the different regions depending on need. From there though, I can't decide whether to subdivide by function or geography.