I'm not a boot expert, but have had significant foot problems solved by good advice.
Stiffer shank in the boot? Might help with the foot bottom soreness. Hot spots are created by friction, which is usually a fit issue. Boot fit has as much to do with foot volume as it does with length and width. That is best solved by picking a brand whose general volume standards match your foot. You need a good boot seller to advise on that. Socks can help some, but have their limits.
I've never heard of anyone who used Lathrop complain. Probably out there, just not in my universe.
A temporary solution for hot spots is duct tape wide enough so the edges are not in the area that is slipping. Reduces friction, but is not a great long-term solution.
I too use lathrop and sons insoles. They work great. I have used them for the last three years. I have only had one time where I have gotten hot spots and that was on a hike where I gained and loss about 9500' in 12 miles.
As far as boots go the most comfortable pair I have found are the Lowa Tibet GTX.
