Hi Jacques,
Well, I'm no electrical engineer or programmer, but I would imagine at the very least and electrical engineer would need be employed, and one certified in the area of material lifts. Depending on what feature(s) you wish to add, you would have to provide original electrical drawings specific to your existing lift. Overlays as we call them are pretty much a thing of the past. Taking an existing older system or just a basic lift that travels two or three floors with no indicators or other desirable features and wanting to "upgrade" to enhance or add certain features/operations is expensive. But if you've got the money, I'm sure there is someone who can/could do it, as long as there is no infringement on local codes/regulations regarding alterations to the original design certificate . The better bet or investment is to have a package deal from a lift mfg'r that shows the user exactly what he wants to see or use in your case. To take your "goods hoist" and have it display or function like a modern type OEM freight/material lift is asking a lot in my opinion. But it's just that...my opinion.