A single ANT device would be able to transmit at 40Hz (your nodes), but a single ANT device cannot receive from 40 nodes at 40 Hz (your master). The most channels a single device has is 8, and the max bandwidth of the combined 8 channels is about 200 Hz. Possibly you could use multiple masters with each one talking to a few dedicated nodes, but that would be quite a complex solution.
This is the sort of thing I would recommend mocking up with ANTWare II first, but you would need a large number of USB sticks / hubs to test it out properly.