So, about these custom Castle and Keep designs.....
I hope that you are not limiting yourselves to 1 castle, 1 keep design for this publish. Also, I'm glad it is you all choosing and not me.
After scrolling through the list of pics on the Stratics thread, I am blown away. Some of those designs are incredible. You've probably already thought of this, but maybe you could take the top vote getter and then add say 8 more to the tool.
Hell, you could probably add 24 of those designs to the tool. That could generate some variety in housing!
If you added a large number of designs, for the next publish instead of doing castle/keep, maybe just choose a different size foundation and turn the community loose on it. That way when someone clicked on a foundation size, they'd get a list of different pre-built houses for that size in addition to the basic plot.
You could use the community to really help you fill out the housing tool. That would give people who aren't into house design some ready to go architecture. Let people get a nice house without having to figure out roofing in UO.