Fields should be tags, as they are closer to the concept I would like to use them.
This has to be done in two steps (well, it doesn't have to really, as I am the only user and do not have any data in the application, but I'd like to do it none the less as practice):
Create the new tags model, write a tasks that copies the data and deploy all that
Delete the old fields model and use tags everywhere where fields where used before.
In the grand scheme, I like the idea of having the possibility to add different media types to the application. However, for now, it is just making things more complicated to develop.
I will focus on just having articles in the app for now and making them work properly. The other media types can be added later on with more care.