Using Custom Controls, you can assign AE Lock to the shutter half-press (you can do that on the 7D, as well).
Didnt know this....
Why is this not the default setting?
So doe sthis mean, if I choose spot metering and center AF and lock AE the way you have described, that I essentially have a 1 D series exposure lock synced with the AF, albeit only center point?
If it were the default setting, you'd have to take the shot - your metering would be locked until you took the shot or it timed out. You may not want AE Lock with anything but spot metering, anyway, I suspect.
Don't have my 1D X or 7D with me, but in the custom controls for the shutter button, I think the options are metering + AF start, metering only, or AE Lock. I think if you assign AE Lock to the shutter, you need to assign another button (AF-ON or AE Lock) to AF start. Not sure, though - I'd have to check.
But on my 7D, I'd often set spot metering, and I use back-button AF, so I'd center the subject, hit those two buttons (which are conviently close) to lock focus and exposure on the subject, then recompose and shoot.
Where the 1-series with AF point-linked spot metering has a big advantage is that you can take a burst with spot metering on an off-center subject, instead of just one shot.