So here is our situation.
We have an ancient software called UltraC which we are running in a Virtualbox VM. The VM is Windows XP and then UltraC runs inside that as a DOS. One this software we have 30 alarm systems connected from different customers. In my search for a replacement I ran into Home Assistant and I am wondering if you can use this software for multiple alarm locations. We also need to make it simple enough that our Emergency Dispatchers can easily use it. We use 2 way radios to send information from location to dispatch alarm computer. So it goes from Sensor->Panel->RTU (Ztron M1708)->Location Radio->Dispatch Radio->Controller (Ztron M1700)->Alarm Computer
This system uses FSK for the data transfer. We would like to eliminate as much middle as possible but create an easier to use system based of ModBus or other easier things.
Would like your input on the subject. The alarms are intruder alarm, fire alarm, voltage monitor, etc. So anything where there is a closure of circuit. We are not doing any video.
So I guess the question is this. Is Home Assistant something we could use to upgrade our current alarm setup so we can leave the old system behind? The thing we like about HA is that it is off the grid. We don’t have to upgrade it if we don’t want to.
So a potential scenario that I can think of is to have Sensor->controller->local HA->Local Radio->Dispatch Radio->Dispatch HA Computer
So would like any input on the subject. 
EDIT:
So after discussing it further. We can update our Ztron Controller to do ModBus. So now it is just a matter to program HA so that all the information from the different RTUs are correctly interpreted by HA.
Ones we have the old system converted over, we want to find replacement for the Ztron controller and it’s RTUs because they are quite expensive and there is no hardware development on that side of things.
So I’m wondering if someone can point me in the right direction for how to get something like this working on HA?