All this to re-engineer a 40 year old system is ridiculous. I know it is possible, an old Westinghouse hand could do it. But you are messing with group operation, maybe fire recall, if it has that. Call electrodyne or a similar company that has engineers and insurance. The Hotel really needs to upgrade to a whole new system. An Overlay will address the problem but it really isn't the best way. Doing this as a Technician should not be an option.