Well, since he intends to earn something off of this, and information is infinitely replicatable at no cost, "showing" the product would somewhat devalue it.
The system he describes is what I aspired to create at one point, albeit in a space-4x environment as a PC game. Never got anywhere with it though.
The key is to use only as many rules as required by the ongoing game. I'll pick a related existing case, IL-2 Sturmovik, the flight simulator. You can toggle each and every realism rule that the simulator can provide, tuning the game to your desires. You can fly in full-arcade mode with invulnerability, but with realistic bullet trajectories and blackouts. Or in full-sim mode with unlimited ammo and fuel. In this system, if I understand it right, it's largely the same.
There may be systems in place for easy logistics of every mentioned level - military, economy, trade, and individual combat and adventure. These systems may be made to mesh together, allowing to only use as much of them as you require. Say, you're an adventurer and you suddenly waltz into a cave and defeat a big guy who turns out to be the leader of a large tribe, which promptly makes you its new leader. You'll be able to keep the individual adventure aspect, but a new system will be layered on top of that should you choose to issue orders to your subordinates. Conversely, you'll be able to omit the adventure aspect and just play by the governing rules, establishing trade routes and dealing with wars on a larger level. A single system encompassing everything is indeed a very big, and very good investment. In a way, Dwarf Fortress will become that someday. Adventurer skills, making an own fort, rising to power... it's all there in dev_next.