Currently I have found that people don't really have any reason to come down to Lower Sanctuary unless they are involved with The Covenant of the Pure, so as a means of enticing people down into our slimy waters I think it would be a good idea to perhaps add a few old quests down there and maybe even alter them slightly to align with the current scenery.
I remember there was an old ooze quest in the canal wards which might be cool to bring back? Maybe the old temple of Hoar quest could return and an NPC could offer some coin to clear the crypt of undead etc.
Also it would be nice to see a few starter quests in Lower Sanctuary and maybe give new characters the option to start in Lower Sanctuary again.
For myself and those I've talked to, its because of the Covenant that its rarely travelled by those outside of it. They have been quite prominently aggressive.
If quests did return, they could be slimy variants with someone inside trying to persuade them to join the Covenant, and people find out the 'quest' they were on was really a conscription trap :)