Yes I understand. I actually did two videos that show how what you’re looking to do can be accomplished. I’m not sure if you’ve checked them out:
Give them both a watch and I’m sure you can extrapolate from the videos what it is you’re trying to do. I think the best way to do this would be to segregate off the cell or “work zone” behind a NAT, this way you can standardize private IP addresses behind the NAT and never run out. Then on the “public” plant side you handle the routing. Both these videos will give you a good explanation and visual of what I’m suggesting.