My paragraph of analogies:
Sounds like the house was completely built onsite and the customers were ready to move in before any building permits were obtained and the foundation poured.... In other words, that large of a system should have been engineered and system integrated by a professional, long before anything was purchased. But instead, mismatched parts were purchased, probably based on price & availability and the system cobbled together, in hopes it might work right out of the box. I realize the OP was handed this mess and now heat is being applied by "upper management" to make it work. I would have told them "Not my circus, not my monkeys". Especially if this is a volunteer position. Good luck to you. Try to talk them into contracting a professional to sort this one out.