What we are specifically interested in is for our quad-copter to be able to detect and maneuver to avoid (maneuverability is based on our custom algorithms) objects flying towards it with great speeds. A paintball gun projectile for example. Regarding the coverage of all possible directions, we are not concerned whether or not it will be achieved with one or many sensors. What we are interested in is if a sensor that can do that exists and is suitable to be mounted on-board a drone.
Consider a pellet going 100m/s, it will cover 25m in 0.25sec, let's say your drone is 0.5m in size, and detection time is zero, you still need to achieve 16m/s2 (1.6G) acceleration instantly to get out of the harms way -- which is a bit unrealistic for the contemporary drones.
Take a 60FOV camera, with 4k resolution, this will give you about 2000 pixels vertically (or horizontally), which @25m become about 12.5mm large (one pixel), which is not enough for the reliable detection. 30FOV camera might work with 6mm pixels @ 25m, but you'll need plenty of them to cover your surroundings. And processing all these 4k images is not going to be cheap or fast.
You cannot detect a fast flying object @25m unless you use high velocity cameras (upward of 100fps), which again drives the processing cost higher.
IMHO, your best bet would be to go either in the direction of creating a large reinforced drone with high redundancy that does not care about pellets and can keep flying after the hit, or creating a fleet of match-box sized randomly moving drones that work as a swarm and don't care if there are a few casualties. Check out this: https://www.youtube.com/watch?v=9CO6M2HsoIA