Because of my crappy connection, my game does this to me anyway.
But I think the idle kick thing could be a good idea. And maybe even an hour would be too long. I think a half hour of idleness would be warrant enough for the boot. You're right, there are a lot of people who just idle in the public maps, (myself included) and in populated areas, it does create lag.
However, I can see how a certain group of users wouldn't want this. Seeing as they have to be in-game but may have to multitask on other things. Such as, monitoring a forum? I think it'd be a win-lose situation when considering the entirety of the game's population.