Revise the base AutoCAD code to support multi-core processors for ALL operations - not just redraw, regen, and rendering. It is almost impossible to buy a single core CPU anymore and quad core is becoming the standard. Therefore with a 2GHz processors you only have a 500MHz CPU when running CAD. This is equivalent to CAD performance in 1995 (20-yrs ago!).
I understand it is a ton of work to re-code, however, it would give MASSIVE performance increases across all the verticals; including Civil 3D.