The floor plan proves to be poor during the shell construction

Everyone dies on their last day, not before. You can only mess up the chances of the second and third house when the time comes. The only ones nailed down to the first house are the builders who build a house that is explicitly unsellable or only sellable with a financially damaging discount. As you can read here in a current neighboring thread, there are even interested parties for a sky-blue suicide house in Posemuckel, provided the floor plan is not a labyrinth. The next house will probably come about when the kids have left the nest.

I am also torn back and forth... we are building once and there will not be a second time. I have the feeling of having missed the chance to build the house that would have been almost perfect.

Let's be honest: are you inside the house or in the garden during the summer? And in winter? What do you do then? Do you want to sit inside during the day in the sun? To be honest, I assume you're no different from us sun lovers: in the bright months: quickly finish the day's work inside and then out into the sun, meaning the garden. In the dark months: the day's work goes a bit slower, canning, cooking, playing with children, no matter if or where the sun is. It's dark in the evening anyway! With 3 kids, you usually carve out time in the evening, right?

When you work from home, it can really make a difference. Our apartment faces WNW, so in winter you already need the lights at 3 o'clock. Whether that's the case with the specific floor plan...
Actually, it was mainly about the differences in the sun position between early October and winter. In October, it changes a lot, so when the OP comes in two weeks, he might not find the light situation so bad anymore because he's in the shade anyway.

When you work from home, it can really make a difference.