Man, I like me a good Johnson, especially the LMG variant. Apparently you could load an extra 5 rounds with the 20 round magazine via stripper clip, so possibly have that extra 5 rounds as a selling point to use it over the BAR variants? Could also load the thing with just stripper clips on the side, would take longer to load though.
So a premium squad suggestion is to have the larger magazine variant for a paratrooper marine squad. It was mentioned to exist in: https://www.youtube.com/watch?v=vf40tHdKmno around 6 minutes in.
That is all, have a gud un.