Dropping the attempt to steal Lolths Drow Portfolio as 11th level action, trying to expand/find ways to expand this plane.
Also takeing more mundane actions to quell disguised intruders, eg Gems of True Seeing given out, large areas permanently Hallowed (that have good or neutral populations), Permanent Detect Evil spells cast on people so they can see trouble makers on certain sides who do not belong ie (on good and neutral sides), using magic (9th level or lower should deal with sanitation problems shouldn't it?) to solve Sanitation problems.
Remove populations who don't mind living underground to the underground, the drow and deep dragons will go. Keraptis and Drow should know some stuff about working with stone as should Deep Dragons. (At least I hope they do, otherwise I'm gonna have to spend some time repairing Keraptis's Mazes when I have some free time before they kill some poor soul.)