Would it be feasible to use separate operating units instead of whole business groups? With one business group and 30 operating units, you could have Manager1 seeing only purchase orders in OU1, Manager2 seeing only purchase orders in OU2, and BigBoss seeing purchase orders in both (if that would ever be a need). This separation works for all the finance modules, projects, purchasing, and sales orders. If you want to isolate inventory, you could have 30 Validation organizations, each inventory organization can only see the inventory items enabled in its validation organization.
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