I actually think it is pretty powerful and NOT just with RoL/Hope decks. FFQ decks can also create an army of kamikaze Fireflies with Light Flux, let alone Unstable Gases are in the same element with Fireflies and a combination of upped and unupped FFQs and Fireflies with UG and LF in the same deck could be deadly. Luciferin also becomes OP with this card, lol. Imagine a deck full of Skeletons, Graveyards, Luciferins and Light Fluxes.
Actually, I don't think it is OP, since Hope shield loses power with each LF played and 3 damage per creature is like Fractaling 3|0 Sparks that deal spell damage, something not very great. I would have voted for this idea, but there are other ideas I like slightly more than this one.