Um, just a few quick words from me.
If conceal carry is in question, this method will PROBABLY only work with vests or jackets. Food for thought.
Some states won't allow fixed blades to be concealed, or even carried at all, but will for folders. However, folders are usually slower and more difficult to draw than fixed blades. The "quick access" sheath for folders is suppose to address both of these issues. This makes it somewhat of a niche concept.
I completely agree with the set of guidelines for a serious personal defense knife. However, I completely disagree that the Delica98 fits that guideline. Besides, anybody who finds serrations threatening will likely to find a the "quick access" sheath concept threatening.
YMMV.