You can install apt-btrfs to get snapshots when installing thingsm and run "eatmydata apt-get install <x>" to remove fsyncing. Of course, you would be out of luck if the power went out in the middle of the installation, but it makes things much faster.
You can revert to the snapshot so there isn't really a problem, although that can be quite finicky and probably take longer to setup than the time saved avoiding fsyncs.
Note that btrfs will be just fine on unexpected power outage - the filesystem will just contain some random combination of old and new files affected by the installation.
