let's ignore the "bla-bla": I'm very happy that App::Link has been integrated into core FreeCAD, so let's focus on the next step, and one of the next steps is assembly. Please, also consider that the question is complex and that we need to discuss it !
today, in v0.19, it is possible to build assemblies using core App::Part and App::link functionalities. It is possible to import external files/objects/parts into an App::Part and to place them using manual placement, or the "Transform" tool. It is, also, possible to save such assemblies and to open them in any core FreeCAD system, without need of external tools (workbenches). All Part and Body objects have "Placement" properties, and once included into an assembly such objects it is possible to manipulate them manually or by the interactive "Transform" tool.
Therefore, my first proposal is to decide (and document) that all FreeCAD assembly files are true FreeCAD core files, and there is no need of separate file format.
This, of course, has many implications:
- the A2+ file format is a dead-end. But its solver seems very good ...
- the Asm3 file format is a dead-end. But its SolveSpace solver seems quite good ...
hum ... but this also questions whether these good solvers can be use with some other file structure. So, in short, and before going further, I'd like to separate the assembly file structure from the placement of objects in the assembly geometry.