I think you just made a better case for having everything in UTC. Instead of having to remember multiple offsets, one for each location, you just need to know your current offset to get a sense of relativity (i.e. "ok, that occurred an hour ago") and the correlation across different locations and sources takes care of itself.

I'm not saying that a log aggregator is not needed, they are still an important of any system as your 3rd paragraph clearly explains, but your 2nd paragraph actually makes the case for keeping everything in UTC regardless.