For the cranes... do you have large magnets? You could build the cranes like some of these:
http://www.igg.org.uk/gansg/12-linind/dock-ch.htm Then attach them with two magnets in the rotating base. The magnets would have to be fairly powerful, I suppose, but I haven't worked with magnets much so... i dunno. Even without the magnets, a good solid pin would keep them in place and maintain mobility.
As for the scaffold, I think you should make two scaffolds that are physically separate but fit into the scaffolds like they are connected. Build a solid base for the two new scaffolds with the scaffolds on wheels that are glued to the solid base. That's my idea for those, then you could move them where ever you wanted them. I think the gargant should be what connects the two sides, though.
PS: It looks awesome. I would like to 3rd that face on the top.