Wow! This is such a thorough post!
I slapped together similar (but much less impressive) take on this theme very recently. I use VNC for remote access rather than SSH'ing into my home network directly. Do you opt to just forward a port on your router and send it to your pi's SSH port? I wasn't sure how risky that would be or what options exist for that.
Also I noticed you mentioned a water sensor at the end, I did a similar project for that as well after I had some basement water issues. I just got a couple of super cheap humidity sensors and had them take a picture of the scene and email it to me if the sensors thought they were submerged. Great minds think alike! :)