Can I provided 3.3V regulated directly to the BBB
Does the device offer support for providing non-5V power? I would expect not because the BeagleBone Black is a USB host.

While this is an answer of Y for an X, it was requested as such:

You probably want multiple point-of-load regulators with a higher distribution voltage to avoid having a lot of current across long wires at 3.3V. This would allow the use of thinner wires to distribute a higher voltage to each cluster of devices, then use regulators (switching buck regulators recommended) to supply 3.3V or 5V as required. Typical nominal voltages could be 12V and 24V, depending on the regulators chosen, power demands, and power supply availability.

Using a higher supply voltage would also decouple the mobile battery voltage from the supply voltage of the numerous devices.

Additional advice: try to keep power and signal grounds separated to avoid too much current flow in the shields of your signal cables between cameras and switches.