The strategy of Colossus/early HR is being dictated by the map. Normally I build quite a few cottages to keep my economy going, we do not have that option here. As you said yourself, the primary goal is to get a toehold on the mainland. Once we have done that, we can move our cap, and go hammer mad. We will have to tech Cavalry to conquer al of the AI, so we will always need a good commerce base.
So, in the meantime, with our lack of decent production, we will struggle to get numerical superiority. With lots of commerce available, we should instead aim for technology superiority. I still like teching towards Mace's, most of the techs are essential anyway. If we can tech towards and then whip a decent force of Cats/Maces we can get our toehold before Longbows.
@ Colossus:
You are right that it is not the end-goal in itself.
We want it because it will allow us to expand to a large number of island cities. So, I agree that we don't want it at the expense of REXing, the trick will be to manage both. This is why we want 1 settler, at least, out before we build Oracle. After Oracle, ideally the cap will be building settlers/WB's for a while and city 2 or 3 can then build the forge/colossus. I don't think we will need many workers.
In a tiny island zone, I think we can expect a maximum of 3-5 land tiles per city. In HR, once each city is at pop 10, it will be working 5-7 water tiles, giving an extra 5-7 raw commerce. Multiply this out to 10 or more cities, and you can see the benefits.
@ HR
Yep, completely agree. As long as we do not research Hunting, we can abuse Warriors to grow very large, this works very well when every extra tile gives 2f 3c. I do disagree with the 'No Courthouses' part of the strategy, islands will mean higher maintenance costs.