Thanks for the compliment.
A mock-up in pine or similar would work well. Since the screws are metal inserted into the wood you won't get a lot of wear due to wood on wood movement. Not sure how long it will hold up to daily use, but I've built plenty out of softer woods and wouldn't blink an eye at building at least a prototype out of pine.
I'm a bit curious as to the lumber availability there in Germany. Also, do you have a good choice of sawmills in the your area? If so, I'd contact one and see if they have some common stock that they'd like to get rid of at a good price. That's how I get the majority of my prototype lumber and secondary lumber for drawer sides and interior parts of furniture.