Bathroom Size - 2 Floor Plan Options, Costs

This is the dashed green line!

Who came up with the idea to put the toilet in the middle of the house without a floor drain and without any drainage at all?
Where does the wastewater go?

I don't see any additional cleaning effort due to one or two more square meters.

Where does the wastewater go?

Pyrolysis would be an innovation! Or you install a narrow flush tank and the drain flush with the wall. That's how we solved it in the guest toilet.

Yes, the flush tank can also be built into the wall and the pipe can then run vertically downwards. I see no added value with the larger floor plan. However, there is also no difference when cleaning, because only more floor area is added.

The question is also where the additional space is taken from. I would prefer the slightly larger version - but not at the expense of a smaller children's room...

Yes, you can also brick in the flush tank, and the pipe can then run vertically downward.
I don't see any added value with the larger floor plan. However, I also don't see any difference when cleaning, because only more floor area is added.

Yes, of course. But a) you draw it in, just like the drain, and b) I consider a drain in the middle of the house to be reckless. Anything clogged under the floor slab/bend is, as the word already says, crap.

To the OP: my advice is toilets on the exterior wall. At least the waste pipe, and place the toilet with the shortest distance accordingly.