One point, among the many, that jumps out at me from the discussion between the tribes of Gad and Reuven and between Moshe is this - the impression of being unified. Of feeling, and knowing, that everyone is contributing to the whole of the nation equally.
the whole problem with their taking the parcel of land in the Eiver HaYarden was that the rest of Israel would think they do not want a part of the land, and that they are trying to avoid fighting in the wars alongside the rest of Israel.
Moshe is concerned the people will see them setting up their homes while they themselves are about to embark on a lengthy battle to conquer the Land of Israel, and he knows that they will come to resent Gad and Reuven. They will call them shirkers. They will say they are living off our backs and blood.
The whole discussion, and the agreement they worked out, was based on this premise; to avoid a situation where the rest of Israel would resent them, even if only because of a false impression.