Third, if you need to 'upsize' later its a lot easier to just put in a
larger breaker than putting in new or more wire.

If you wire for higher ampacity, then may as well install appropriately
sized breakers and outlets, etc., at the time. Otherwise, unless wasted
the extra money for the higher-rated outlets until that unforeseen maybe
never to happen time in the future, placing simply a larger breaker may be
fine for the wiring itself but not for the outlets, etc., ...

True but I was thinking of being able to add more outlets to the same line.
Example when I bought my last house there was one outlet along the wall were
I wanted to put my entertainment center I had to use 2 power strips. No big
deal there because nothing was drawing much power and very few of the items
were on at any one time. But what if in the future things need more power?
I'm guessing they will. Its a lot easier to put an outlet or two on an
existing circuit than it is to run an entire new line from the breaker box.
Who know what we will need in 10 years. Its a bit more than 10 years old
but the house mom lives in had a total of 6 fuses when it was built!! I
think when we remodeled it we added 6 more circuits, with fuses so you can
tell that's been a while ago.

I might change my mind when I start building. But right now its going to be
an over wired, concrete dome with metal studs and fiberglass backed
wallboard. I'm a bit paranoid about fire so there will be very few
flammable building materials used in it.