I need to have another application installed on the same host used for BE2016. This brings SQL Server 2014. Is it possible to dump the data, deinstall SQL Express and import the data to SQL Server to use it for BE2016?
Before you change from the default BEDB, I would suggest that you think about how you are going to recover the BE Server when you are in a DR situation. It is not so straight-forward when non-default BEDB is involved
We strongly recommend NOT installing the BEDB into the same SQL instance as production databases. This is due to the extra complexity needed for recovery in event of loss of the SQL instance to some kind of disaster.
Because of this (and the next information is more of a personal opinion based on the above point) I would either always keep the BEDB inside its own instance OR if I had to share an instance would only share with IT systems that would typically rebuild their data content if needed (i.e. HP Insight Manager, WuSS, Live Update Administrator etc) I would definitely not share an instance with departmental or operational production databases that might be used (as examples) by HR, Finance or Sales etc.