Brep is just a polygon mesh. Speaking as a person who has to juggle them occasionally at work. So the current Blender modeling options are isomorphic to those

Brep is just a polygon mesh. Speaking as a person who has to juggle them occasionally at work. So the current Blender modeling options are isomorphic to those of a BREP modeller. All it would need are some more constraints. What is lacking, is the parametric history.