At this point the cool kids on the DIY forums have worked out exactly how to build your own powerwall equivalent using LFP cells bought directly from China. It's enough of a savings to make it a worthwhile project.
My personal favorite is DIY Solar Forum. I'm more into LFP batteries and solar for my RV than for my house, but here is a direct link to their DIY Powerwall subforum: https://diysolarforum.com/forums/diy-powerwalls.25/
As cool as that sounds in a certain sense, I would be shocked (no pun intended) if doing so wouldn't void one's homeowner's insurance. There's no way in hell I would put so much concentrated energy in an amateur pack anywhere near a home.
