The basement doesn't necessarily have to be underground. The basement level would have lower ceilings and the front door on the main main floor would be reached by exterior stairs, like the picture below.
I dunno about a toy house, but in real life the thought of a kitchen being sequestered away down in the basement doesn't make the thought of cooking fun at all!
more like slavery! In real life I'd prefer a wide and open kitchen that is incorporated into the surrounding aesthetics of the household they're cooking for.
As for the playmo house, I agree the old victorian houses are THEE AWESOMEST houses ever, even though there is always room for improvements. Having a basement section with lower ceilings might work I suppose. Or to avoid having to lower the celiings, maybe the house could come with a deeper foundation (maybe looking like a side of a hill or rock) so the basement level can stick up halfway above the foundation, and halfway below the foundation. (so it's windows would be at groundfloor level. When you look out from the kitchen window, you'd be able to see someone's feet if they were standing directly outside the window)