We used to do this frequently for analog systems, and had good success with KVM equipment from BlackBox. The particular components will depend on the exact requirements. A similar system with DVRs involved 2 monitors at the front desk, 1 mouse & keyboard, 2 video extenders, 1 KVM extender, and 1 KVM switch. This allowed both DVRs to be monitored all the time, and alternate control of each for screen configuration or investigation. Also local KVM at the DVRs for configuration and service.
I have to say, though, that I am happy that most of these systems have been upgraded to IP now and we don't have to support these installations, because they were often a pain to troubleshoot if something stopped working, which happened several times over the years.