Hi J,
is looks like much better. Now i understand the issue with Terrain FEATURE.
FALLOUT is one of them also.
Your code runs after the effect from the original nuke.
So the nuke has already change for example the FEATURE_FLOOD_PLAINS to FEATURE_FALLOUT.
And than the planetbuster code remove the fallout once again.
Now the feature from begin is lost .....

This is also the reason why we can't see this with FEATURE_ICE on water. Because no fallout will created from a nuke in water terrains.
mmh - a solution will be to edit the original nuke code to create no fallout on terrains with FEATURE_OASIS or FEATURE_FLOOD_PLAINS for example, is this possible ?
Very cool the rivers stay at terrain now!
One more edit.
After the planetbuster hits a city this results in ruins and there is a message in gamelog
that the impacted Civ has destroy the own city .......
Can you remove the gamelog about this and the city ruins ?
This will be great .....