Usage of the engine for other projects
There's so much potential with the core. A few examples off the top of my head:
A Computer/Console Tycoon, where you build your own PC/console, customize it, choose the internals, and compete against competitors. The performance of sales would be based on the cost you're selling it for, how much heat it generates, the reliability, the issues with certain components, the performance, the looks, etc. Perhaps a few twists, such as a fatal flaw in the built in software discovered leading to a patch, many machines being shipped in for repair because you didn't put enough into testing to fit the complexity of the machine, flaws in the BIOS causing it to overheat and detonate the Lithium-Ion battery causing millions in damage to your company, etc.
A medieval weapons/armor designer. You would have to design armor and weapons, choose the material, etc. Again, a few twists such as orders by kings. If your armor performed poorly for what they were designed for (scouting, skirmishers, etc), you would be exiled. This would severely dampen your profits, as an entire kingdom would stop buying, and your reputation would plummet. If you recover from that, you could, for example, retract your company into a single kingdom and grow exponentially in it, and make such well designed armor that you would have enough reputation to expand (profitably) again.
Seriously, the designer alone allows so many possibilities.