I've thought of a problem with going for the Great Wall.... Charismatic means that Stonehenge might be particularly useful for the +1 happy (I normally like to build it anyway if we're not cultural because it makes it so much easier to put cities in good long term positions and not worry about resources only being in the 2nd ring of the BFC. And Stonehenge normally goes very early - before the great wall - so going for an early great wall is very likely to mean losing Stonehenge.
There's also a question of the great person: The Great Wall gives a spy, and with this setup, the spy will be great for exploring our continent (since the scout is unlikely to live long). But with no AI contact the spy will be useless for anything else. On the other hand, Stonehenge gives us an early prophet. Combined with Oracling Code of Laws, that means an early shrine, which will be pretty helpful to the economy, so helping us to get to optics/astronomy more quickly.
Now I'm wondering it'd be that stupid to prioritize Stonehenge over the Great Wall...
I have no experience in isolation games, so I tried a couple of them with Big_Small island maps (on Emperor) but I haven't really gotten the timings for Astro bulb/tech strategy right yet.
Seems to me that after worker techs and BW you have to go writing, then go priesthood to Oracle CoL, and have a GS ready around that time to bulb Philo as well. That should cover the GP generation, but so far either my tech rate was a bit slow or I got only very few cities by the time astro comes. I think after writing you have to go alpha to build research; I tried going math first (to chop Oracle more efficiently) but now I think alpha is more urgent at that point. After that, it is tempting to build temples, maybe lighthouses, maybe even some forges, or some extra cities, but I'm not sure they pay back in time for a good Astronomy date...
I'll need to experiment a bit more before I try this BOTM.
There's also a question of the great person: The Great Wall gives a spy, and with this setup, the spy will be great for exploring our continent (since the scout is unlikely to live long). But with no AI contact the spy will be useless for anything else.