I searched recently to replace Sketchup with MoI but, even that MoI is more powerful under the hood, still lacks a big feature and this in my opinion is the possibility to make models parametric, like Sketchup Components, or Rhino Blocks, or Inventors iLogic, etc.

Personally I think that if will be implemented this sort of parametrization in MoI will take this software to the next level.

As I can see there is already support for scripting, so maybe just a GUI to link the logic with the objects and make the objects to behave accordingly will be good.

Also driven dimensions and constraints from other parametric softwares are powerful to achieve great results.