Basement living versus more living space on the ground floor

If the suitable plot is not an option, then the wrong house on the hillside plot is the unsuitable solution.

Why? The plot fits perfectly. Simply put a basement under the bungalow, done. There wouldn't be any discussion with me. Go to a turnkey provider, have it fully calculated. Then there's a number. Then ask what the filling costs. Then there's another number. Compare them. Done.

Why? The plot fits perfectly. Just put a basement under the bungalow, done. There wouldn’t even be any discussion for me. Go to a turnkey provider, have it fully costed. Then there will be a number. Then ask what filling costs. Then there will be another number. Compare them. Done.

You seem to have a clear overview. Finally someone who agrees with the OP. For the garden access there will then be an outdoor staircase, as already seen today in another post.

can you please properly draw the plot into the development plan? With such an extreme slope, precise planning is essential. Or is there already no budget left here for a ruler? Alternatively, a plot plan works as well, where you position the sections so that there is a reference point that can be found in the development plan. We don't know the project, only you do so far.

I am randomly building a hillside house with a basement living area, with an exterior staircase, retaining walls, embankments.

I am randomly building a hillside house with a residential basement, with an external staircase, retaining walls, embankments.

Well, then I probably haven't come across the design yet. Link me where I can see it. But the design of the OP has nothing to do with a residential basement.