Very fun, and nicer than water damage or an invisible wall. As well as the planned stuff you mentioned, it'd be cool if you could make areas with fewer mines, giving a chance to pass through safely.
updated the extension,
additional minefields can now be enabled.
max level for mines can be set (so you can build over it, default every block in the minefield area acts as mine trigger)
shows black decals on the indestructible blocks (openspades needs a patch for this to show up, patch is submitted & pull request is made)
new update, added command for mapmakers to show coordinates of blocks destroyed (also disables spawning of mines)
and made the bounds inclusive on both inner and outer fields.
Very cool learn_more! Only thing that needs to be done is to popularize the minefield maps on servers... Or add the minefields in existing maps - yay that would be awesome...
Spoiler:
"Aos is not dead"
"Take on the legends if you dare." -Only on BnS.