Jumpstart on development of application for building construction

Dear Forum members,
I have a requirement to develop an application to allow potentially non-technical users to build structures visually (buildings, roof structures etc) from a selection of standard “modules”, which are octagonal shaped 3D units. These modules would be dragged and dropped from a library selection into the working space and “click” together (hopefully utilising the constraint system in Blender) in various configurations to form complete buildings. The process is not that far from what the Lego Builder software from a few years ago did. How and in what configurations the modules could be assembled would be governed by a set of “rules” (eg cannot click more than 10 modules together in a line etc) to meet structural constraints or the like.
I am time poor and trying to rationalise the best software to use as a base for this development, before spending the significant time necessary to investigate each further. I would be very grateful for any thoughts/comments as to the appropriateness of Blender for this task and any issues that might be problematic. My immediate questions would be:

  1. Can constraints be set up as required?
  2. How do I implement the “rules” I describe?
  3. Would the resulting application be web accessible, with user login managed, perhaps even with different user types able to do different things in this 3D building world?
  4. Would there be any current projects or code snippets and the like already underway from the Blender community that could be used or provide guidance to this project?

Thanks in advance,