just make it 1v1 national regimental cup, that's what i would like to play
2v2 is very hard to realise with such an activity right now. Plus even just a 2v2 cup (international) would win some team with two stacked regiments like K-KA and 15th YR as example (since 91st wouldn't play with K-KA), so there's no balance as well.
Just make it 1v1 NC Cup. And allow nations like Belgium, Ukraine, Ireland, Serbia, Bulgaria, Austria/Switzerland and others to merge with somebody. We can make 8-10 national regiments easily, NWL rules, group stage then playoffs, can be a great national cup though.