Once again, I don’t understand why everything is being so rudely torn apart.
It’s not rude when you honestly mention the negative issues instead of sugarcoating everything.
In the end, you also ended up with a completely different house with different dimensions. You have shaped a wrong rabbit out of meatballs.
And whenever it’s said: build for the now, and if you can no longer manage the stairs later, you can’t live in the house anymore. That simply isn’t true.
No one is saying or writing that. You just have to do a lot of work in 20 years anyway. And then you can see how it fits.
At least some dimensions should be right.
If he didn’t have a (former) guest room on the ground floor, he really couldn’t stay in the house anymore, but as it is, that still works quite easily.
Well, then try setting up the ground-floor bedroom for an (older) couple. That’s neither fish nor fowl. And that’s not rude, but to the point.
And then simply address the OP’s question. Because he wants to reduce the hallway area.