Merge layers, while retain the original properties of the objects

Hello everyone.

I am looking for a way to merge layers, while keeping object as they are.

The situation is I usually receive huge architectural drawings, and I am required to export them to 3ds max for arch. visualization (this is not a drafting problem).

The drawings are usually messy.... lots of layers.... lines and polylines properties are not set by layer.

So the question is simple: A lisp or a way to:

Merge layers while keeping the object properties as they are (color, line type, thickness etc)

Thanks in advance.