for me, the following workflow would be an optimum:
(link between files by filename, time ...)
Is it possible to have such a workflow with the available tool?
Or, if not, what is the way to propose such an idea to Adobe?
LrMobile is designed for a camera -> computer -> device -> computer workflow, or for images captured on the device itself. It's not really designed for your camera -> device -> computer.
That said, for your raw+jpeg workflow the key optimisation is probably to "apply (copy) the preliminary edits (done on the tablet) now automatically to the full res images on the PC" and I suggest you look at this post about my Syncomatic plugin - Syncomatic and LrMobile. It was never something I ever suggested, but people found the plugin was ideal to automate copying the preliminary edits for large numbers of pictures.