Obviously, I didn't read your post carefully, or I'd have seen that you referenced an Emerson-*like* design. Sorry.
Regarding the concealed fixed blade, I agree: legality must be a consideration. I'm dressed casual most of the time, and carry a fixed blade openly. I don't find that I get too many weird looks. I'm not recommending this for all people in all jurisdictions; but, for me, it resolves the issue of folder failures.
Again, I highly recommend the Sebenza, if your heart is set on thrusting with a folder. Not cheap, but then, neither are your digits. YMMV.