When Hyroen and I were discussing this card, we talked about what to do for the upped one. We felt that adding +2 boost to photons was iffy, because now you can fractal free 3 attack creatures.
However, I think the idea of changing the boost to +2 instead would be preferable to making it stack. One reason for this is so that it functions the same way as nightfall. Another is that making it stack is probably worse for the photon issue than upping the boost to +2 would.
So I think an option for the upped one is to follow eclipse and up the cost to 4 and the boost to +2|+0.