I would like this feature. It would be nice to have a graph showing stockpile over time, per colony, per system, per sector and a total for the whole empire. With time limits like last 6 months, 12 months, 5 years, 10 years and whole time. And ideally it would remember the last settings too.
It would also be nice to have the same for wealth.
The +/- displayed is only based on the most recent sub-pulse tick which can change and fluctuate.
I think this would be much more useful if it showed the change for the whole of the last production cycle, that way you have a single timeframe to work with.