My guess, if I am understanding your network correctly, depends on whether your 900 mHz link are full duplex or half-duplex. If they are full-duplex, I envision that when you transmit into the "hub", the hub transmission in turn brings up the slave link repeaters that in turn transmit back into the hub, interfering with your own input...
On the other hand, if your links are half-duplex, what you are proposing should work.
Hope that helps.