There is a thread where Non-Ubers are tested for their viability in the Uber Metagame. Its called project Uber. Agreed that there are only a few non-Ubers with potential. The reason for that is the fact that the Ubers are so powerful and versatile, that one has to exploit a niche, or offer something in the way of resistances or typing that can be off use to combat common threats.
As for Block + BP Mew, it has potential. But a lot of common Mew Switch-ins won't really mind being Blocked. Scizor can just U-Turn out, Darkrai can just hammer away with Dark Pulse, etc. Mew really needs that free turn to get off a Substitute/Taunt for protection against such threats and Status, and when you think about it, Block really reduces your versatility, taking up an ever valuable moveslot. You would be reduced down to Block, Baton Pass, then you either have to risk dropping Taunt for a Boosting Move and Rock Polish, or Only passing a single stat. Blocking an opponent such as Darkrai or Scizor, in summary, isn't a good play. You may catch something like surprise and get your recipient in wit minimal harm if played properly, but IMO, its far too restrictive. I also doubt you'll get time to set up Everything and Pass away, considering everything in Ubers is pretty powerful. However, dropping Baton Pass and Stat Boosting and chucking up Dual Screens, I think is a better set in conjunction with Block.
Oh, and I'm not sure if anyone has tried this, but Gallade is quite useful in Ubers. I use the following Set (though I can't remember EVs) as a Trick Room lead (though I'm sure Gallade has other uses other than setting up Trick Room)
Gallade (M) @ Lum Berry/Focus Sash
Careful/Sassy
-Trick Room
-Brick Break
-X-Scissor/Night Slash/Shadow Sneak
-Destiny Bond/Taunt
It basically plays like this;
Deo-F: Trick Room, then 2HKO with X-Scissor (suprisingly, people forget Gallade resists Superpower, and you'll live Shadow Ball suprisingly well, maybe even enough to sometimes live extremespeed)
Deo-S: X-Scissor to break Sash/Avoid Taunt, then Trick Room if not taunted, attack otherwise
Kyogre: Run away
Groudon: Trick Room, then Destiny Bond. I think I packed enough defensive EVs to live an EQ from most Non-Life Orb Groudon
Darkrai: Trick Room, the OHKO with Brick Break
Mew: X-Scissor and if/when it BPs and if/when taunt is gone, Trick Room (it'll usually pass speed), then Destiny Bond to kill the threat, unless it can be removed otherwise)
Mewtwo: Can't do anything except Selfdestruct, because you'll get off TR, then Destiny Bond it for the KO. Feels good to kill Scarfers =)
Shaymin-S: Run Away (Yet again). If you have Shadow Sneak and Focus Sash, you may want to attack, to break the Sash, then switch to a resist
Giratina - O: Run... unless you want to take your chances if you have Night Slash
It handles most special based Ubers without boosted Shadowballs fairly well, but it still is quite frail physically. I can't remember the EV Spread because I deleted the team, but it has enough Attack EVs to OHKO Hasty Mewtwo with X-Scissor I think, as well as Darkrai and will always 2HKO Deo-S with Max HP (Screen versions can't even set up)
