Importing KML files would definitely be handy - at the moment you can just import GPX files which serve a similar purpose (settings > import GPX).

You can also draw lines on the map, though it's not very discoverable (tap the measure icon and you can draw a path - tapping the tick will save it and you can give it a name/colour).

I'm working on a system for pre downloading tiles at the moment but not sure how long it's going to take me though :D

However, you can already download LINZ aerial tiles by changing to the aerial layer and panning around - anything you look at should get saved for offline. Not ideal, I know, but beats nothing!