Ideally, we would use a system that at the point of digitization, an object is assigned a globally unique identifier. At this point we could then trigger the CREATE event in a Fedora 4 system, likely a separate one that is only intended to store event data and provide the API/REST services as well as SPARQL interface for queries. The GUID would then stay with the digital object through its lifecycle which could be a significant amount of time before it is prepare for digital preservation. This is why we would use a separate Fedora 4 to store this data and would continue to do so even after ingest into the digital repository.
The problem at hand is simply that our workflow is not to create an immediately ingest digital content into our Hydra repository. We could configure other systems to store this data and in some cases this is taking place. But this puts us in a position of having some event data stored in plain text files, some is stored in microsoft excel/access and then some is stored in various SQL instances. So as others have indicated, we do need the ability to bring in event data that occurred prior to ingest of the object into Fedora.
It could also be possible that we use this separate Fedora 4 as the generator for the GUID making, what seems, like a smooth integration point between the instance that only handles event data and the instance that handles digital preservation. It also avoids a potential infinite loop. An event to say that we updated the record effectively updates the record which triggers an event to say we updated a record, again. For very sensitive materials, the level of event logging we would perform may be just that granular.
The reason behind using a separate system for logging events is a fundamental principle of not having a system audit itself. So using a separate instance helps to maintain this separation, in my eyes it is separating the prison guards from the inmates, we should not trust the inmate to count themselves. But more importantly, we may want to track inmates that are on their way into the system, not just after their arrival.