On the inside of the box for the yellow castle (#6075), there's a nice little alternate castle tower with a bridge and a ramp leading up to the front doors. It's the one in the bottom, center of this image: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=234504
. The back half of the tower is hinged so that the whole tower opens up as seen in this image: http://www.brickshelf.com/cgi-bin/gallery.cgi?i=234503
For years, I've had my little yellow castle in this configuration (plus a gate tower at the front of the bridge with a drawbridge instead of a ramp), but on reading your post, I decided to try and reproduce it with LDD. You can download the LDD file from this link: http://designbyme.lego.com/en-US/Gallery/default.aspx?parameters=2||16a0463f-7ccf-433a-a3a2-58ccddbf7f10
I know LDD isn't the greatest, so instead of a yellow castle with grey floors, it's a grey castle with black floors. There are also numerous minor differences due to the bricks that were available in LDD. Notably, I used a bunch of these guys
, when they hadn't been produced when yellow castle came out. Also the main doors are brickbuilt, and the very top of the turret is speculation, since it is not shown in the box photo. I've always suspected that this tower couldn't actually be built with only the bricks from 6075, but I'm not sure and am not going to try to find out.