On Fighting Arceus, you definitely want to mention it checking Extreme Killer Arceus. It's the only Arceus forme that can actually hit super effectively with it's STAB. Lum Berry Extreme Killer is not very common, actually: | Item | 11.6 | Lum Berry | . It's not a total counter, I agree, but it's a great check and should be mentioned. As for the "anti-metagame" thing, I'd say conclude with that. Fighting Arceus is actually pretty underrated, and can punch great holes in teams with its Calm Mind set and is a great glue for stall teams.
I'll leave Grass Arceus for barry.