In order to reduce overall costs, as you're replacing older conventional fire alarm systems with new addressable fire alarm systems, it looks like the wiring in each building is going to be reused.
One thing to be aware of is that in reality, the addressable input modules at each tamper switch and the addressable zone modules in the panels are the same bottom-line devices - no matter what they're called, they're zone input modules that convert the conventional signals sent from the tamper switches into an addressable form that the panel uses.
For the upgrade, the difference between the two types of modules is the location (by itself not important) and the number of modules inside a single module-assembly (single module at the tamper switch and multiple-module packages at the panel - by itself not important).
The real issue isn't the location of the modules for the retro-fitted fire alarm system, at least right now; the real issue is how you have to deal with changes to the fire alarm system at a later date.
Later, to add other devices like flow switches, addressable modules may have to be located at a tamper switch. If the modules are located at the panel, it may be more costly to later add addressable building wiring that can be used for the additional modules. With addressable modules at the tamper switches, adding another module next to the module already there is easy.
There may be other issues with older wiring styles in the tamper switches (where the wires land on the terminals inside the switch might have to be brought up to date, for instance). These issues would be corrected as part of the upgrade if the modules are located at the tamper switches. On the other hand, these wiring issues might not be corrected if the modules are at the panel. Later, with new tamper switches or other additions, modules might have to be installed at the tamper switches anyway. At a later date, especially if the wiring has to be upgraded, that would possibly be a fairly big cost.
Right now, though, the cost of the system is probably lower to go with the zone input modules at the panel. Later, if something has to be changed, the cost will be lower if, at this upgrade, the addressable modules are installed at the tamper switches.