Hi Sam,
I have tried to not interject too much on the "Wofati" posts, just so folks like you could "hash out" there Ideas. I have written a few times about the framework styles possibilities. There are several traditional (and mixed) modalities that could eliminate all the "iron" in these structures, as fossorial architecture has been "timber framed" (usually a post and lintel format) for millennia without any modern hardware...so we know it is very possible to do...
I won't go into to much detail of a critique, as that hasn't been requested other than to say you have a generally nice design...and...a great use of SketchUp modeling!

You can eliminate the "oblique bracing" as well, if you chose replacing it with an older and more easily facilitated horizontal modality.
Regards,
j