Multiple industries near a station.

[LaChupacabra]

How about something a bit simpler such as a minimum distance between industries, so that the probability of 2 or more industries falling into a single stations coverage area is reduced.

Setting minimum distances between enterprises is a matter of NewGRF, not of the game itself - the game should definitely not impose any solutions here. Besides, if such a function would be used in the case of very complex sets like FIRS, it might turn out that on smaller maps many enterprises could not be created at all, because everywhere is some industry which accept the same cargo - it would be very bothersome. For example, consider different ports that accept the same cargo. They look very good when they are right next to each other. With this limitation, such layout which create large ports would no longer be possible.

Would it be possible to partially solve this problem by simply equally splitting the incoming cargoes between the available accepting industries.

Sharing supplies between multiple enterprises would have its advantages. The problem would still be that the player would sometimes not be able to choose only one recipient.