An easy improvement for Lightroom 'Import' feature would be if it remembered images you had already imported and 'deleted from disc'.
Currently your rejected images from pervious imports are detected as 'new images' when you put the memory card back in.
It would be a simple matter to keep the exif data from deleted photos (e.g. file size, camera, lens, date and time taken) in an 'already rejected' table in the database, then when they come up again on a memory card, Lightroom knows this file WAS imported but 'deleted from disc'.