The problem I see with all this is that Grandfather is TL35, last time I looked, and if you think a paltry TL17 civ's efforts to attack him, or even LOCATE him, for that matter, is going to be noticed, well, you're deluding yourselves.
I can see that maybe a TL17 civ starts to muck things up, maybe they start tapping into the pinching-off of space that's required to make portals work at TL21, and maybe he's worried about his former race the Droyne coming to an inglorious ad sudden end and TL18 would make bad things happen to them... Whatever.
I can see the possibility that he might want to stir up trouble, but there's no way anyone's gonna be able to touch him, and the only people that even SUSPECT he exists are people in a universe in which he is simply a piece of a game.