Hi,
I have read your attachment file. For completing this project, I guess I need about 5-7 days. It can be faster, If we maintain a good communication. If you are not everyday using freelancer platform, we can communicate with another platform, but first let's get in touch via freelancer messenger.
I think I can design this board bellow 10x10 cm, its still a rough imajination, 2 layer board is enough. For display, If we want a long life battery we can use more power friendly LCD module like Epaper, But it's up to you. All of sensor you propposed doesn't need a special treatment in design, so it would be easier for me to design it. For reading 4-20mA analog input data, we can use a single 250 ohm resistor or even we can use op amp as current sense, we can decide it over discussion. For thermocouple, Actually I don't have any experience using it, I think you have already try that, I will refer to you.
I will use Eagle for this PCB design. I have use it since 2012 and has done a lot of PCB for Hobbyst, Robotic, Industrial, IoT, and military purpose. I have Bachelor on Electronics engineering, So, I know how electronic work, and I know both Firmware and hardware part. I always following Design guide when design critical design like SMPS,RF,High speed digital design, etc.
Lets discuss the detail over messengger. I will be waiting for your response.
Best Regards,
Rijal.