You've got to be kidding - every single project would take twice as long, cost twice as much and deliver a product that none of hte users actually wanted. Oh, wait. That happens now...
Each country gets to design a system. Everyone buys THAT system.
Germans build the tanks and wheeled APCs.
British Build the Carriers.
Italians...umm, the staff cars umm. Oh Attack Helicopters.
British Build the Light tanks (ala CVRT).
Austrians Build the Assault Rifles.
Germans Make the Machine Guns.
French....buy Excoets from them.
Dutch make the Frigates.
Swedes make the FACs
Norway makes the Subs (or do I have that backwards with the swedes?)
Go from there...