Hi,
the chat system exposes the various options to fire an event across the network, you can send to a particular user or to ALL, so simply send that event to ALL. it's one or the other here, there is not in between as far as I know.
I think we have a problem of vocabulary, what do you mean by "target a specifically instantiated object", either you want to target a given instance across the network ( sharing the same photonview id) or everyone.
could you explain how the chat system should be modified to fit your need? cause essentially, the chat system is the best way to describe communication between instances and players. So could you give me a use case? like USER A sends a chat to self or USER A sends a message to ALL USERS etc etc. If we can implement your use case within the context of a chat, then you'll be able to apply it to anything else, and instead of sending a chat message you'll send what's relevant.
Now, if you are looking for streaming, streaming can only happen within the same photonview id, there is not other way. for any other mean, you'll have to code it yourself, like passing on the streamed values to other players within the same instances ( using regular events, as you do without photon being involved).
bye,
Jean