Hi Jed,
Given your examples, I would agree that a camera without a spot meter can achieve the results of a spot meter. Anywa, here are 2 further points for your response:
colour issues can be simplified because most of the time, you can find something approaching 18% grey to meter off
An expert can probably call out that this object is 1 or 2 stops off grey, but I can't (at most I can guess the direction but not the exact amount). If this is a case, then the solution seems to be to spot meter off something approaching grey in the scene. A large dark cliff - find a tree growing on it to spot off. A black lighthouse (just an example

) - hopefully the lighthouse keepers house next to it is grey.
Having said that, I concede that there is a quick and dirty way - if the scene is predominantly light or dark, just shift 0.5 stop in the correct direction and bracket both ways 1 stop. That should give you the correct exposure. (if I ever get a digital camera and stop paying for film I might just do by doing super 6 frame bracketing 1/2 stop each). I think Shadus has grasped that

So spotmetering is not essential.
(Of course best is in birding where a light coloured bird and dark coloured water usually cancel each other out)
spotmetering can tell you that contrast is too high and maybe you should recompose to include less of the offending element / use a ND grad if possible / etc
I think this still holds. You have usefully provided a technique of using an average/matrix meter to figure this out by, eg: pointing the camera at the sky, which presumably can be applied to other elements of a scene as well (provided they are large enough). But the point is, you working around a lack of a spotmeter. In effect, you are increasing the size of the 'spot' (a spot being an area of equal illumination) to fit the size of the sensor.
Anyway, your mention of the zone system was useful, it made me think whether I'm advocating spotmetering or a stripped down less-cheem version of a zone system (which does not necessarily require a spotmeter, though there seems to be an intuitive fit between the 2). Maybe you can share your thoughts on this - metering for landscapes
