Today I was asked if there is any issues in installing NAV 2017 on a Server/Computer that already have an existing installation of Navision running.
I can hereto say No, there are no issues if you remember one thing.
You must make sure, that the Instances uses different ports for the Client, SOAP, OData and NAS Services.
You will not be able to have them running at the same time if they uses the same ports.
Otherwise I have not seen anything that could cause problems.