Completely restoring the game state from the savegame
In the very early days of the freeciv project debugging was made significantly easier by the fact that the bugs were much more often reproducible from the savegames - the bug you encountered during regular run could be reproduced by loading previous savegame and doing the same actions as in the original run.
It required some work to maintain that state of things - that loading the savegame would produce the same state (especially that of the random number generator) as what it was during the original run. Eventually it broke more permanently, over twenty years ago - I remember that I had filed a bug report about the final breakage before moving to another city in early 2001.
Maybe we should revisit the issue. It would be very beneficial to have that reproducibility working, and it might be more feasible to fix now than back then. We could, e.g., include more data to the savegame these days, without the size of the files becoming a problem.
Even if we couldn't have such a support enabled by default, having it at least optionally would be a big help. Use-case here is the autogame testing. If my testing environment would have such a feature enabled, I could (in many cases) reproduce issues from the latest savegame within minutes, instead of each debugging iteration taking twelve hours to run from the beginning of the game to the point where the issue occurs.