If they interact with each other, then wouldn't any "wave" collapse?
The particles leave the event in a smooth wave. Then they run into other waves, or each other, or just the background gravity fields. This perturbation should cause them to clump together. So in short order the smooth wave would become large blobs of gravitrons more akin to raindrops than waves. And without anything holding them apart, might not some of these clumps condense into some sort of ... I don't have the words for such an object. I wouldn't want to get in its way.
I think what you're trying to describe is something like 'confinement'. I'm not confident that a massive graviton will necessarily lead to confinement, neither gravitons nor confinement are that well understood.
It's a converging series; instead of getting a clumping you may get a slight mass increase. These new gravitons that modulate gravity between existing gravitons are not 100% there, so they do not contribute that much.
The particles leave the event in a smooth wave. Then they run into other waves, or each other, or just the background gravity fields. This perturbation should cause them to clump together. So in short order the smooth wave would become large blobs of gravitrons more akin to raindrops than waves. And without anything holding them apart, might not some of these clumps condense into some sort of ... I don't have the words for such an object. I wouldn't want to get in its way.