I was referring to a 2 wire circuit. Putting a dry contact device that maintains a short after polarity is reversed is very likely to blow up an IDC or cause a power supply to trip a PTC or pop a fuse.
On a 4 wire loop, you would use a single supervision relay per zone, otherwise it won't work properly. I doubt that anyone would come close to exceeding some of the largest supplies out there (10A) for an analog fire zone, but if that's the case, normally the move is to get away from 12V and go to 24V. Most analog panels will allow up around 300 ohms of tolerance in addition to the EOLR value (and most panel EOLR tolerances are either 5 or 10%) so that works out to typically around 6.5 ohms/1K feet. If you size up to 14 or 12 to factor in a loss, the resistance will drop to 2.5 or 1.5/1K feet. Factor in splicing and similar, you're still in the MILES of cable before you would need to worry about cable resistance, however voltage drop would affect the detectors operation downstream in addition to the supervision relay.
This is all hypothetical, because honestly, if you get to a fire install that size, and honestly even up around 20 or more devices, I'd start to move towards addressable and if needed, interconnect the two.