I agree with many of the sentiments here. I, too, dislike the large wall panels. Sure, they make great corners, but why bother when you could fill in with bricks? The Helm's Deep set did a nice job of filling in angles with the 1x2 cheese wedges.
I would like to combine a few of these ideas and see Lego come out with a line for the Castle series akin to what they have done with the City Creator sets (Palace Theater, etc.). For instance, they could sell a single tower on a baseplate. You could probably keep it to $100-150 for the tower. Then a section of wall on another baseplate, maybe $80-100. Gatehouse on 1-2 plates, $150-200, the great hall or keep for $200, etc. Make them so that they can snap together with technic pins. Then someone could buy just what they wanted and fit together their own castle--long walls, short walls, a keep, no keep, etc. I know that something like this will never happen probably due to low market share (look at the Nexo Knights, trying to modernize and popularize the castle line), but it would be my dream.
Oh, and while I'm dreaming, how about a castle with a real gatehouse? The gatehouse was usually the most important structure of the castle and would encompass several sets of doors and a portcullis, plus most times a drawbridge out front. Most of the castles that Lego has made have a porcullis and some doors if you're lucky; otherwise, it's just a portcullis. Maybe I request too much realism in my castles.