I'd be averse to putting a gigafactory in Japan because
1. Seismic (think earthquakes and/or Tsunamis)
2. Geothermal (think volcanoes)
3. Atmospheric (think typhoons)
4. Oceanic (think sea rise / erosion)
5. Mineral (think lack of local resources)
It's just too vulnerable an area to develop in and they have to ship in any missing minerals for production.
If Tesla is already dependent on Japanese production they should spread their next factory to another geographic location to reduce risk.
Let Panasonic build their own copy of the gigafactory there if they want but let Tesla focus on new ground.
I have to disagree, and vehemently, with everything that both you and Chickenseveil have to say against Japan.
Not because they aren't true statements,
ceteris paribus, but because they aren't relevant.
Now, Japan may be - and has been - in a 25-year economic funk, but irrespective of that, Toyota, Panasonic, Honda, Mitsubishi, all the Japanese
zaikai have been able to grow and prosper quite well, thank you very much, with all the baggage you have cited.
To address your points more specifically:
0. Land prices (Chickensevil's point)
* a 5mm or even 10mm square foot facility, with its ancillary land, takes up as much space as does
any other large industrial campus, of which Japan not only has manifold examples, but there are some antiquated facilities that could be retrofitted for the purpose.
1. Seismic.
* Much of eastern (="southern") Honshu is a seismically quiescent terrain - about as likely to see an earthquake as is Sparks, NV.
2. Geothermal
* Very little of Japan's overall land mass is so susceptible. No more so than, say, Fremont is from Mt. Lassen.
3. Atmospheric
* Typhoon activity is relevant at best only to very specific sectors or east/southeast coastal areas. Akin to saying do not consider North Carolina because the Outer Banks are hurricane-prone.
4. Oceanic
* Ditto above.
5. Mineral
* Which is why Japan never will rise to become an economically important entity......ditto Netherlands, or Singapore, or........