It doesn't make it easier to change bases. If the company needed an additional body in a base they just put it in either domestic or international.
And if having two divisions created more jobs that increased the opportunities to switch bases.
With cross utilization of reserves between bid statuses the inefficiencies have probably been significantly reduced.
There are significant benefits in the 757/767 flying with two divisions. International was heavily favored by commuters for its longer trips and commutable on both ends. Domestic was less commuter friendly.