I've looked through a bunch of books and pdfs and cannot find a very specific section that exists in one of them detailing new types of purchasable/buildable alterations for a construct.
Specifically the section had an option for a cockpit so you could pilot your construct like a mech as long as it is at least one size category larger than you. I also recall the same section had another augmentation which transformed the chest cavity into a storage space.
Where can I find this particular augmentation and the section it was in? It could be within 1st or 3rd party books or possibly either Dungeon or Dragon Magazine.