I ran a deck like this. It actually hit pretty consistently for 150, either every turn or every other turn (running a stage 2 with it is clunky, you want to be able to bust an ozone by turn 2).
You DEFINITELY need a starter; it is the only way the deck has a chance. Azelf X gets rid of weakness, or you can also run bubble coat. SSU and Seeker is a must. I had Banette in my build as a Mewtwo counter, but it probably isn't necessary. Junk Arm works wonders with it, since you can get back Legend Box and pokemon rescues.
As far as starters go, I would run Jirachi. Sableye is good, but it doesn't have free retreat. Run Regice to discard Legend Pieces and energy, and run Dialga PT 5 to put them back on top of the deck for a guaranteed Legend with Legend Box. It's an effective engine, but isn't too competitive. Mostly a fun deck.
Oh, and donking tends to be a problem with this deck. I got donked twice in a row at BR's; had I just survived an extra turn, I would have gotten RDL rage going quick. Alas...