I would like to be able to see ethernet up/down messages in the logging.
you could make a script for this 
That is ridiculous solution - to waste resources on script for such a trivial stuff.
Handling Ethernet traffic is what Mikrotik is best at, and also most lacking at.
Some of us who have been doing ethernet stuff since the days of BNC terminators, Personal Netware, Windows-for-Workgroups, Winsock, and putting drivers in your config.sys. Ethernet is so important. We can depend on other companies for good radio link choices if we want, but we depend on MT for ethernet interfaces and it’s features if we want to network with MT.
I don’t think such a script would waste more resources than any other solution. Anyway, we will think about this.
I take having to schedule any script to execute each second to check any status is wasting resources. Events or triggers, which are native way to handle such needs were promised long time ago but still not provided.