2 Sheds
So what you're saying is that you should change your callsign depending on the service you're providing, even if you are sat on a LARS position shall we say.
I think not - the grounds for confusion in that scenario are too horrendous to consider.
When I'm sat on Radar I'm Radar, no matter what service is being provided. When I'm 'Radar Off' I'm Approach, and can only give a FIS. It is up to the PILOT to understand the limitations of the service he has requested, not up to me to change my callsign.
I Suggest a read of MATS 1 APP E 3.1
CM