I don't think in-app purchase is a bad idea, but I'd argue you go down the route of:
DEMO + Purchase Full Game to unlock routes, don't sell routes in batches, it will ruin the flow of the game.
If you actually think you can generate merchandise, it would be a nice idea, but merch is expensive to get prototype first versions for molders and printers.
The idea you have is someone with a large base capital and can afford to burn about 50k annually to pay for wages and other outgoings.