Construction Lines/ Drafting Tools

What Feature would you like to see included within TaleSpire?
What does it look like, how does it work, how is it used. Paint us a figurative picture.

Construction Lines and other Drafting Tools (Circles, squares, cubes, spheres, etc), would allow users to draw persistent shapes on the map to plan out designs while building maps. The visibility of these shapes could be toggled. This would allow someone to quickly sketch out a map to begin to fill it in with the various set pieces TaleSpire provides.  

What situations would this Feature be useful?
Descriptions, examples, interactions with existing features - whatever you can think of to get your idea across!

In the most basic implementation of this feature, it would simply be a way to sketch and mark up a map to make construction easier. A more full featured version could allow various TaleSpire props and tiles to click to the construction/draft tool lines instead of the main grid.

Additional Thoughts/Details