>as I'm currently trying to become clear on what to make out of Clonkonaut's suggestions.

Mh, I really don't know whether I like the idea that you can extent your castle from the inside. But I do like the idea that you can change the type of a wall or add/remove doors later (that is, first you build a tower - and if you extent your castle further you can remove that inner tower if you need to).

>Any specific ideas?

Thinking of Profpatsch's/Clonkonaut's suggestion: Special buildings could have some requirements. For example a fire/furnace could always produce smoke that you do not want in your castle. Give the players the ability to build a chimney through the roof of a castle part and hilarous castle design is ensured
- you have a "smoke-room" where you direct all the smoke instead of building the furnace on the highest level of your castle? Sure, why not.
- you use the chimneys as a duct for your electric lines? Sure, why not!
I was probably mainly thinking of stuff like hatches (like in CR), though. I really don't know whether I like the idea of Clonkonaut's noses, since you could do stuff like that already with loam (and actually require some thought/effort from the player if he wants great castles) - adding the graphical representation of a nose automatically could still be done.
I will probably have to think about that a bit more (what other kinds of castle parts other than walls, doors, towers, (hatches, chimneys) make sense)