Feature request: Lockdown which groups can be viewable in Zendesk Talk.

As it stands right now, our technicians are in multiple groups for different purposes and workflows.  We have specific groups set aside that are prefixed with "Phones" which are intended to be the only ones that calls are routed to.  In our Number Routing, these are configured properly.  However, if a technician is in one of the Phones groups and another non-Phones group, if another technician wants to escalate a call to next tier, they are capable of transferring to a group that is not intended to receive phone calls. 

This plays havoc with our data collection and our group management practices.  We have implemented protocols and procedures to encourage our technicians to only transfer to the applicable Phones groups, but human nature being what it is, mistakes happen.  Having the ability to limit/restrict which groups can receive transfers would be a huge help and prevent this from happening.