The EU does not have the competence under the treaties to make Ireland abandon its corporation tax set up.
A new treaty would have to be agreed by all EU states and Ireland would certainly reject any such move.
It doesn’t matter what any EU nation state leader does because they must obtain a unaminous agreement to change taxation policy from all member states.
This would mean a new treaty , one that requires consent from all member states.
There is no other way to do this.
Germany and France can indeed jointly harmonize their tax regimes by common agreement.
But they can not affect Ireland’s tax regime under current legal EU provisions.
Those provisions on taxation policy being the sole prerogative of each member state can not be changed without a new treaty.
That’s my understanding of the position.