I'm not an engineer nor have I worked with seismic concerns but I have a relevent concept that may be worth some consideration.
Since you want to use very thick side walls, much thicker than an ordinary foundation walls, perhaps the posts could extend through the first floor to the basement floor and if the foundation could be thickened with pilasters to meet the tf perimeter, then the posts could be bolted, bracketed or strapped to the foundation to acheive the cantilever. Embedded wood should be avoided and a monitored solution seems prudent. I have no idea if an engineer would approve.
Happy brainstorming.
