Wouldn't make much sense either. Operationally, you have a group of five European NATO members in the North operating submarines (UK, Germany, Norway, Netherlands, Poland - ~27 subs) and five European NATO members in the South (France, Italy, Greece, Spain, Portugal - ~27 subs). The only submarines "inbetween" those are the French SSBNs.Can't see the German and French doing the same with subs.
Do people even realize that A400M is first and foremost a procurement programme for the EATC, which will be its sole dispatching user? And the EATC does have that little coat of arms with all that blue and the 12 stars...I particularly like the A400M example, just imagine the chaos of having 27 members in Brussels managing that program.