Except that aside from Taunt Mewtwo (and it has a ton of other options that are quite possibly better) and Psycho Boost Choice Specs Deoxys-F, virtually no uber uses Psychic, so that weakness is mostly irrelevant. Steel Arceus isn't dumb.
Giratina is ugly. =(
Unless you're really desperate for a Dark resist, I don't really see the point of Fighting Arceus. I'd rather use Bug Arceus to resist EQ and hit all the Psychics save Lugia hard (and you'll be hitting Lugia harder than Fighting would).
Turismo, I really don't see why the "uber" tier would be so different from the other tiers. At Smogon, we don't determine our tiers based on whether they are allowed in the Battle Tower. Your tier is determined entirely by the highest tiered Pokemon in your team. If I have a Salamence, Geodude, and Pidgey as my team, I have an OU team, despite having Pokemon from lower tiers. OU, UU, NU, and uber are all just names for tiers. Having Rayquaza, Geodude, and Pidgey gives me an uber team because it contains at least one uber.