Here are a few pics of a breakaway blacony idea that I had a while back. Since the castle is modular, using connector pegs and holed-bricks, I felt it only appropriate to do the same for castle wall features, such as balconies, bridges/platforms, and maybe even elaborate entry ways. 
Keep in mind that this is just a rapidly assembled prototype. As you see, I didn’t even complete the wall example.
Above is the inner view of the balcony. It’s high enough for a minifigure, but NOT if he is a knight with a feather on top of his hemet! Obviously I need to raise the height. I’ll test out others, like Wizard with pointy hat, as well.
See? Breakaway!
Below is another balcony prototype, but it is an open-style. I will either use constructed “wooden” double doors or two sliding curtains for the interior. It’s more appropriate for a Royal audience chamber or some otherlarge public room (dining hall, perhaps?).
I really need to follow your lead on the break away balacony thing. One of the peskiest issues with design I have is simply putting the figures in after the fact. Too short doorways or other things getting in the way of stubby fingers having to put pressure on the awkward legs of a minifigures… sucks. The way you’re doing it is smart though because you can just take it off, put a figure in and snap it back together without an issue. You can even do small redesigns on breakaway bits too which must be damn nice.
One other reason I like what you’re doing is because you can design more “secure” looking places to put figures instead of having an open area that wouldn’t make sense on a real castle. No need for larger open air type spots.
I have one more idea for a removeable piece that is similar to your bridge crossing idea for displaying minifigures. Well, two ideas, actually. Suspended bridges that lead from one tower to another. The second is “rope bridge”. The first one would be “stone”, so all gray pieces, with a few color accents, and maybe even small recatngular planted with flowers (more color!). The stone bridge either be constructed as an open-air “breezeway” type, or walled-in for more protection.
The rope bridge or log bridge with rope or chain railings, would obviously be very open and airy. Hm…perhaps instead of making it modular, I can just make it part of the landscape, such as the bridge over a ravine.
Anyway, once I a couple of working prototypes, I’ll post some photos.