Where are you located? Approximate....just a state or region would help. Where you are located determines what is needed for housing. What matters in Alabama is different than in Maine.
Did you say 20 miles? Did you mean 20 acres? 20 miles would be the size of some entire counties in Missouri. That would offer a lot of room to expand!
It also sounds like you have some experience with houses already. How are these constructed and how are you managing the litter?
It seems you have two directions to go. Continue adding smaller colony houses of various sizes and space them out. Depending on your location, you may be able to throw together some stuff using those that will cheap and adequate. Or, go all in, consolidate and build one bigger house that puts all your eggs in one basket. That is going to be a bigger investment and one that is not easy to back away from if this venture goes south and you want out.
For the larger house option, you could look here for some ideas.....
https://www.ag.ndsu.edu/extension-aben/buildingplans/poultry
These are a collection of older style chicken houses dating back to the 30's, 40's and 50's. A lot of these are getting bigger than what most of us of would consider building today. A lot of good detail, however, regarding fixtures, etc. Sizes for nest boxes, roost bar placements, roost sizes, droppings boards, etc.
After that, you need to decide if you are going to keep them under total confinement, allow them yard time, or allow them to free range.
Yet another option is to go look at similar sized egg operations to see what they are doing. And as this grows, keep in mind local laws that may limit what you can do and where you can do it. You don't want to run into any "Imperial" entanglements.