Sorry Its not Virginia.
It is labor intensive and that's the big cost. It is an inverted T for the finial look. I moved houses already and also Jacked up 2 story barns but a house is a different matter. Much cheaper to underpin walls. I would like to know some of the lengths of the wall and how thick they are.
another foot to two feet would allow room to run some A/C ducts and I'd only want to do this job once. I also have a floor drain to a dry well that would have to be
The big difference is hauling out the dirt in the rest of the basement floor area. I lean towards More depths to get the bang for the buck.
And do you build a temporary support
A lot of that depends on the integrity of the wall itself, cracks/leaning/bulges... Put it this way. You can build a house on pillars and the footer below them are not Huge compared to what it carries. The other aspect is think of the "Arch" effect. Your house has pretty much settled. Unless there is sinking problems there already.
When we knock out a 7' or 8' section of a wall we only need to support the joist under that area because the knock out it is all the way up to the plate. You are leaving the wall in and by doing so you create the Arch effect to transfer loads. To prove My thinking, We very Seldom if ever add to a footer new widths where an opening is in a wall on a continuous footer.
The one 1 third 2 thirds for support is way within parameters of a post and beam structure. Once you wrap the brain around that then it makes structural sense.