Mechanical engineer != Structural engineer... I've been in the industry a few years and you've got no hope.. You're telling me you've designed everything from ground works to electrical/utility layouts and done structural analysis models of the frame etc on your own?... dream on 
I agree and that is why I haven't done all of this on my own. There also aren't many mechanical things in the building other than HVAC. I have a lot of experience in other fields as well along with people who can advise me. I don't claim to know everything, but I know a lot.
Also, there aren't a whole lot of structural things to worry about. The construction techniques are nothing new and any professional drafter would be able to make blueprints for a GC very easily.