You have some options. The MZ2 and VAV controllers may not need to be replaced. Do you have the ability to sell them an AX box with the ASD driver? That's a good fix to any front end problems they are having. They probably either had a Host-8000, Signal, or Ultivist front end that died. Are the controllers still working? I would bet they are. You said they have no budget to replace them, but they could put an AX box in and replace any MZ2's that don't work for far less than a complete new system. They have options, they just need to get the right people involved who have experience with those systems. You may want to sub-contract some of it out and then you look like a hero to the customer.