How about an auto-activate function that toggles it on/off based on if cursor_stack is a selection tool? Or based on if the player is in map view (hm...thought it seems that would need an interface request).

I considered it. But then I realised that it would be effectively the same as having it on all the time so I didn't see the point.

What's the use case? Performance? It's not having a big impact at all when I checked.

More like...immersion/balance. It's a workaround for the weird design decision of not being allowed to build into for anymore and it feels wrong/cheaty to have it always on. (And pressing hotkeys is so 90's :p).

I agree with your point of what you want to achieve. But I don't see how not updating the map when you aren't looking at it would make you feel like you are cheating less. If I claimed that the mod aleeady has the feature that you are asking for then would that satisfy you? You can't see that it's a lie without looking at the source code.