Hello George. Welcome to Terragenesis.
This seems like an interesting product you're developing.
The goal of mass production of tiles would seem to lend itself best to fairly generic tiles with other terrain placed on top.
I'll be curious to see what you come up with.
Interesting developments. I have to wonder though, how well the magnets will stay in place in the foam.
From my experience, eventually the magnets like sticking to each other more than they like sticking to foam.
I would likely have opted for a hardboard/mdf base, but as you mention, the weight becomes an issue.
Each terrain tile is 6x6 inches? 12x12? centimeters??
Each terrain tile is a square shape? And that is why there is eight magnets?
I see three problems with mass production involving magnets:
Expensive because that is a lot of magnets.
Royal pain getting the polarity correct every time/spoilage due to polarity errors.
Wasted time quality checking finished product for polarity.
There is an easy solution to this: Four magnets and four metal plates.
Magnets go on the right side of each corner.
Plates go on the left side of each corner.
Every magnet sticks to metal when assembled.
Polarity does not matter during manufacture.
Magnet requirements cut in half.
You can buy sheets of 26 or 24 guage metal for like $20 (USD) here, they're like 4x3 ft sheets. I get 4x10 sheets at HVAC supply houses for 22.50 with my HVAC contractor's license. Just an idea if you do decide to use metal. Tin snips are like 6 bucks at a hardware store, and any custom sheet metal shop would probably give you small 6x6 inch pieces of scrap for free.
(My blue collar is showing a little bit here)