Think about changes and configuration options to further reduce power consumption:

• Switch off wireless while ethernet is plugged in (suspend device, or rmmod)
• userspace could ask user whether to turn off wifi/bluetooth while not really needed

• explicit "low power/airplane" mode -> turn off USB, etc.

• use laptop-mode more cleverly: don't flush writeback cache after fixed intervals, but wait until the disk has spun up anyway
• userpace policy configuration tool to set devices in power-safe mode.
• use g_timeout_add_seconds in userspace apps where possible (reduce the amount of scheduled wake ups