If I understand this correctly, your bay 1 & 2 solenoids can be operated by schedule with OpenSprinkler (they are just valves or ‘zones’). Pumps A & B, no problem. There are provisions to provide pumps with power when zones are on. You have 2 pumps instead of the standard 1, but that could be worked out easy (Especially if don’t you need them to work independently). Ok – A & B Solenoid controlled by an EC Sensor – home irrigation control just doesn’t have anything like this. More info is needed. How does the EC sensor send information, and can that be mapped? My guess is yes, you’d just need the specification of values that it sends, then build the logic to open/close depending on that info. It isn’t clear if you need A&B to open fully or need to open on a range of values – I’m sure there are valves that do this, but the ones used in home irrigation are just opened or closed (or if you’re unlucky, stuck open by a grain of crap and you come home to a flooded yard).
But my guess is there is something more complicated here. If you are saying the standard system sells for 7k, and the only part of it that is complicated is that EC sensor, then what is driving the price up? Maybe liability considering we are talking commercial farms and fertilizer? Sometimes simple is better – I wish you luck!