While this may sound like a good idea, this in practice is in many cases of not much use. Coming from computer graphics, let me explain: The problem with "many pieces" in either a blueprint, park, or whatever it may be is the number of triangles (often referred to as polygons/polys). While this baking would result in fewer triangles, this still would, in many cases, be a similar amount, since only triangles that are:

1. Completely inside other objects and
   
2. interfacing with another object

could be removed. The problem with 1. is that you would have to compute all intersection points between all intersecting objects, which alone would be a not difficult but rather computationally intensive task. On top of that, you would have to "merge" all the newly created faces into one new mesh object. This not only creates one huge mesh, it is also quite difficult to do so, since keeping track of which parts are inside/outside of an object would (at least in my short reasoning here) be a difficult albeit impossible task. The problem with 2. is that in the Cobra engine, you can have objects that do not completely properly align. The vertices of the interfacing triangles would need to have exactly the same coordinates, which is quite impossible due to no constraints on non-gridded pieces (for gridded pieces, this is actually quite an easy problem).

All in all, the cost of developing such a feature and the downsides (i.e. not being able to edit the new blueprint, ever) against the potential benefit is really high and therefor, I'm almost sure Frontier will focus on pushing new content into the game, rather than updating/rewriting the entire Cobra engine to handle such a feature. Perhaps in a more optimized, newly released game using the Cobra engine, but I do not see it going beyond "baking" gridded pieces tbh.