Nah, an industrial machinery interface won't be liable for ADA suits. Title II of the ADA only covers "the benefits of the services, programs, or activities of a public entity"[0] – public being the keyword.
You are legally allowed to make an accessibility hellscape of an intranet site :)
Many of these systems are an accessibility hellscape for users with 20/20 vision. They're bult expressly to the desires of upper management without any input of the people operating the software.
You are legally allowed to make an accessibility hellscape of an intranet site :)
[0] https://www.ada.gov/regs2010/titleII_2010/titleII_2010_withb....