They're not particularly difficult to lower, as said above you'll need adjustable tie bars on the rear and full alignment afterwards. If anything they're easier than most mk4s as they already have an anti roll bar that goes under the driveshaft at the front. Most mk4s get rubbing at about 50mm.
Camber can easily be sorted with adjustable tie bars and you shouldn't have any Haldex issues. Is he looking at springs and shocks or coilovers?