You shouldn't have 'sludge' in the sump! Not sure draining would be anymore scavenging than suction, unless you also drop the sump pan?
Draining via the sump plug, in many cars, requires the removal of under-trays etc.. The oil filter usually easily (in my Mercedes anyway) accessible from above?
Some cars (AMG) need to be drained as they had saddle sumps, so couldn't reach both via the dip tube (which a few didn't have!) but does anyone know, do Lexus dealers drain or pump?