A couple of ways you might approach this:
One would be to create a track for each of the Input Channel 1, 2, 3, and 4. Then, you can route each input to its own submixes and each of those submixes through a different chain of effects terminating in a different output channel (using SelectableAudioOutput with fixed output channel in each of four tracks)
Alternatively, if the idea is that each output channel has a unique effect on it, you could place each of the four effects (with replaceable inputs) in a separate track and assign each of those tracks its own output channel. Then you could route each of four inputs to a (fixed) effect that is associated with that output channel.