"""""""""""I mean like the faint dashed lines that are displayed in MoI's viewport. For modeling purposes it's good to have some access to those to be able to select them, but do you use them in your illustration work as well for some things or not really?""""""""""

For me it would be nice to have access to these (as seperate object/sets as mentiond). It would allow me to easily reconstruct certain parts. Like the "six legged pod" example. If I needed more of parts of the legs that were hidden, I could use those to generate something at the proper perspective. There are some 2d techniques that can require "seperating" the parts of the charactor/object onto layers/assigments.