Psg 297 Hell‎
Yet another way of handling multiple cargoes is complex, hacky and awesomely evil.

1    Trains try load passengers
2    ‎If train failed to load passengers, try again, otherwise continue to step 3
3    Trains go to first waypoint
4    The closest waypoint is through split to depot/station
5    If train doesn't manage to split, it skips the Go To nearest depot order, and continues to the next waypoint (eventually back to step 3) - because it doesn't see any depot - all depots are behind dead ends (reversers)
6    If a train does split, it goes around the pathfinder trap which tricked into making it split
7    Goes to reverser
8    Arrives to waypoint after reverser, from where it can see a depot
9    Obeys the Go To nearest depot order and refits
10    The cargo loaded is at 0% by getting rid of passengers, so a conditional check skips to Load order
11    Train goes load the cargo with full load order
12    Train drops the cargo
13    ...
14    Refits to passengers and starts again from step 1

‎In more human words:
Trains load passengers first and then enter a cycle of waypoints. The only way out of the cycle is through reversers, behind which are depots and stations.
The trick is that when trains don't see any depot, they skip the "Go to nearest depot" order‎. And on the main waypoint loop they don't see any depot because all of them are hidden behind a dead end - reverser.
If trains manage to split and go to the reverser, then they finally arrive to the waypoint, from which they can see a depot.
They refit in the depot to the desired cargo, which sends the passengers to a black hole and makes train load 0%, triggering the next conditional order: go load cargo.
The rest of the orders is standard, can easily be combined with picking up products, possibly even returning with them to the sideline.