Need to combine 2 flexfield parents in FSG reporting

Within our flexfields we currently have a 4 digit company code and a 6 digit cost center.
The requirement is to report in FSG on combinations of these 2 flexfields.
Eg
GBCT.OPERAT = Manager 1,
GBCT.MANUFA = Manager 2,
DECT.OPERAT = Manager 2,
DECT.MANUFA = Manager 1.

As you can see there is no single manager for MANUFA, so we need a way of creating a parent that combines variations of 2 parents, so Manager 1 parent = GBCT.OPERAT + DECT.MANUFA.
This can be done with account assignments in a column set, however we need to have a facility to use segment overrides with generic FSG reports (no account assignments).