Ah, yes, forgot to check southern warrior. Adding SH is good, but we can't really test AI mids date anyway as we don't know exactly what they have. And we have the wrong AI in the test game. Only thing we can and should test is how soon we can build them, and this requires that no AI builds it first in test game, so I prefer having a test game where the AI doesn't have too much bonuses.
To get some idea of AI mids date, I looked at the general log in some HoF games played on huge/normal speed (huge to give as many AI as possible a chance to build them). Looked at 10 games played with BTS, average date for mids was 225BC (T106). The earliest AI mids date was 675BC (T88) and the latest was 450AD (T133). As we can see the variance is huge and there's no way for us to tell if any given date is safe or not. There is a risk that someone completes them before T90, but it is also possible that they are still available well into the AD's.
In the games I looked at, Stonehenge was built between t42-t62, averaging around t50, so the AI are faster than normal, making t90 mids a bit more risky. But still impossible to tell if we can get them or not.