Add the ability to 'warp' live text
We do the vast majority of our designing in InDesign, so having to go to Illustrator to manipulate text is quite a disconnect to the workflow.
Unless you take the entire layout to Illustrator it is hard to get the text 'warp' accurate to your layout. It involves too much trial and error jumping between the programmes.
We know Illustrator is very capable, but so is InDesign. In fact some of the vector drawing tools in InDesign are far better designed than Illustrators equaivalents - so much so that it is often easier to create artwork entirely in InDesign.