When launched from command line, Nuke will seek EITHER an interactive (GUI workstation) license OR a render-only license. It depends on which command line option you include:
The first seeks a nuke_r (render license), the second seeks a nuke_i (interactive license).
There is no provision for precedence or fallback from one license type to the other. The presence or absence of "i" as a flag on the command line is the determining factor in which license is requested.
You could possibly script a render manager to run the command line that's appropriate for the license(s) you have and that you want to use, but this is beyond the scope of Nuke functionality.
Note also, that a plug-in license type (interactive or render) always follows the type used to license the host that called it. Nuke renders (nuke_r) will only ask for plug-ins licenses of type _r.