The kits that I saw are mostly just hundreds of wooden boards, assembled like Lincoln Logs. The pictures of the interior and exterior just show these boards.
Installing drywall should not be a problem, but the boards slowly shrink over the first year, settling a couple of inches per floor.
How would you install drywall before it finished settling?
Any place requiring 2x6 construction would prohibit this, they are 2.5x4.5. 3x5s?