Are you talking about the X2D or X2E?
The X2E (the small white plastic one) will allow you to enable or disable CE/Coordinator mode. Disabling coordinator make the X2e just-a-router, so it will join another X2e running as coordinator.
In the X2D (the black metal case), nothing stops you from reflashing the Xbee to be a router - or atleast that worked fine years ago when I did this from time to time for test.
The X2 FW really doesn't care about being coordinator or not - that is an internal XBee thing. As far as the X2 FW is concerned, the Xbee works much the same when either a plain router or a coordinator.