Well, one of the Devs just made the mistake of encouraging input, so I figured I'd fire off another one. I searched to see if there was something similar, but nothing particularly detailed and it was in another forum.
Desired features:
1) ability to have my improvements not auto-upgrade when a new improvement becomes available that obsoletes the existing improvement. This is unessential since I can just mod all the obsolete tags out, but it would be nice to keep them since it shuffles the obsolete buildings to the "Old" tab.
2) ability to tell all planets to upgrade all tiles with a certain improvement (say, "Basic Factory") to another improvement (say, "Factory"). It would be a bonus to have "No Improvement" in the "upgrade from" list and "Decommission" in the "upgrade to" list, but not essential.
Implementation suggestions:
1) a checkbox in game options, just like the "throw-away-movement-left-after-autopilot" one.
2) an additional option on the Governor screen called "Planetary Improvements" or what ever sounds ok.
Left list ("Upgrade From") = list of planetary improvements, sorted alpha, filtered by:
- must be available tech wise OR must exist in the empire somewhere
Right list ("Upgrade To") = list of planetary improvements, sorted alpha, filtered by:
- must be available tech wise
- must not be galactic achievement or super project
User hits "submit" button =
- For Each Planet controlled by User
-- For Each Tile on Planet
--- If Tile's improvement = Left list improvement
---- If Tile (and Planet) is eligible for Right list improvement
----- Queue upgrade of Tile to Right list improvement
---- End If
--- End If
-- End Loop
- End Loop
One slightly tricky question is how to determine if a tile is eligible for the right list improvement. Off the top of my head:
- made it through the right list filter
- does not have a "only x per planet" restriction OR fewer than x currently exist on planet
- tile is not currently building/upgrading something else (I'm not sure if this is a desirable condition, but it could get messy to not use it)
Why:
There are lots of times I hold back on researching tech (particularly industry tech) because I don't want the game to auto-upgrade my old improvements and kill my economy with maintenance cost. On the other hand even in a fairly sparse Gigantic galaxy I'm likely to have over 50 planets, each of them with a fair number of tiles, and it would take a LONG time to go through and manually upgrade all my Basic Factories to Factories when I finally wanted to do so (this assumes I've modded out the obsolete-ing relationship between the two). I'm not necessarily opposed to micromanagement, but I rather like to avoid the sort that is not fun and also very time consuming.
Specifically, this would make my all-factories super hive strategy much easier to pull off

Notes:
Yes, this could result in inefficiency, like not making proper use of a bonus square, but I'm willing to accept that tradeoff for this ability (and the tradeoff would not have to be made by those not wishing to use the feature).