We strongly recommend that all upgrade steps are taken when upgrading a simulation system even if some of the functionality is not currently used. This will prevent possible confusion arising from other users in the future.
However it is true that in the case that the GSS6700 is only ever used in a single channel mode (i.e. without PosApp running) then only the feature key needs be added to the GSS6700. The other upgrade requirements could wait until later (sig_gen.txt file and PosApp licence), but this is not recommended.
Please refer to DOC10114 for the complete upgrade procedure.