Ooh, an interesting idea to keep the . I was thinking of this kind of a deck when I was playing Instosis. I made a mistake, playing a sundial on the turn that I was planning to OTK, and saw that even when the turn ended, Chimera's attack didn't decrease by half.
But do you really need 3 chimeras? You don't need them in all of your games (the ones without hax shields), and 3 or 4 wyrms with dive + blitz could two-turn kill by themselves.
A shield might be helpful in taking care of fast rushes, but I think owl's eye or shockwave could work nicely, since you use chimera which has gravity pull.