Forgive my ignorance, but was the failure due to the AT transmission? Do the same issues exist with the 6MT? I just haven't heard of many Z's with engine failures.
I'm sure you could quickly source an engine and transmission. Nissan Unlimited usually has stock. (Near 290 and Beltway 8) So my vote is 1b. If it was my car I'd do that.
You are a better man that me if you can walk away from this sport without some kinda rehab program.
On the flip side, owning a miata is cheap
you can probably sell off your Z stuff and use a fraction of it on a built miata.