Illustrator views / layer visibility
In Illustrator, one can create custom views, which store both pan/zoom information but also, crucially, layer and sublayer visibility information. Being able to choose among these views when importing an Illustrator file would be very useful – imagine turning 40-ish layers on or off manually.
I frequently use different instances of the same Illustrator file in my InDesign work, with different Illustrator layers visible. The ability to use custom views would simplify this greatly.
Ryan G commented
This is exactly my scenario! I have quite a few many-layered technical drawings of products in Illustrator. In InDesign I activate different layers to show various stages of the construction of the product in instructional documents. Being able to accurately import the various VIEWS from Illustrator eliminates the hunt-and-peck layer activation in InDesign and eliminates errors caused by missing a layer.