How the Xbox does it doesn't allow people to install the game to USB then sell the game. Every time you launch the game from your hard drive it asks for the physical disc to verify you still own it. I'm sure Nintendo could do the same. People with basic models will run into a wall with DLC/game patches eating away from the limited internal storage before Deluxe users but eventually, we'll all be in the same boat no matter which Wii U you bought. If the eshop games were cheaper than the physical game discs, I'd probably go that route but they're the same stupid price and you can't sell electronic versions of games after they've been played out. Never understood why digitally delivered games were the same price as physical games bought in a store but that's another topic for another day.
I'll explore the parental lock thing but going on past history, it seems my kids hunt me down to swap discs every 5 minutes because they're bored and want a new game.
Can't wait for Wiiflow to hit the Wii U scene.