In "Age of Mythology", there was a feature, a flag on corner of the screen, that notified you when a worker is idol and not doing anything.
It was a very well needed feature, specially when you assign lots of units to gather some finite resources, and it finishes.
While playing 0AD, I faced large groups of idol workers many times.
also, another flag was used in AoM, that showed idol soldiers, which is a great addition to 0AD as well. considering some soldiers can be used as builders and workers too.
I don't know whether I'm posting in the right place, a Feature request and voting section (for choosing the best ideas) is very welcome. (Perhaps somewhere inside the application ?)
I just started using this game, really enjoying it, thanks to all.