I donīt see the point of using the ground speed mini without autothrust.
Forgive me cosmic, but this seems the wrong way round. The point of ground speed mini is not to somehow enhance the autothrust, or give it something to do; it is to ensure that the aircraft has a minimum energy on a gusty day and a fixed groundspeed. What you seem to be saying is that you can't keep up with ground speed mini, therefore it is ground speed mini that is wrong, not you???
As others have said, the Airbus was designed by lots of very clever people and test pilots etc., are you really saying you are cleverer than all of them? If you fly an Airbus on approach with selected speed, you have disabled the groundspeed mini function and could find yourself near the stall at a very low level.
U