Summary your idea first. You need to make two devices:
(1) Get inputs from elevator controllers and extract information such as floor position, door status, travel direction, custom messages, etc and then send necessary information over serial wires to devices (2)
(2) Display devices that get information from device (1) and show appropriate data to users such as floor, travel direction, arrival light, etc. The device have some ways to set address, set display data.
Those are the big picture of the systems. Detail of number of inputs, outputs, meaning of each, etc need specify after detail discussion.
If my above understanding is correct, you can get full support to have that devices. As 12-years embedded design engineers, I can design circuit, make prototype, developing firmware, testing until you have a working system. And the circuit is an industrial grade design with fuse, circuit protection, etc. It's definitely not a hobby design.
Please have a technical discussion to see how can we make it.
The money bidding is just for reference, we can adjust later after understanding the technical side fully. Basically, you're always pay after receiving work.