Secure Project Expenditure Types by BG / OU

Hi,

I understand that expenditure types are not secured by Operating Unit and they won't be in the future, in that case if we:

1. Have 2 business groups under the same Oracle installation

2. Each having its own operating units

3. And each one of the OUs as its own line of business, so expenditures types are not the same. 

How can we secure the expenditure types appearing on PO, AP and PJC based on business groups/operating units? personalization might be an option? trasnaction controls..? hmmm, any other thoughts?

Thanks,

GEO