I don't know about "fundamentally unsound," but it seems like an odd mix of strategies. the basic idea of 1 ... c5 is to stake out space on the queenside in preparation of an advance there while at the same time contesting the center; if black follows that strategy, 2 ... b6 will lose a tempo if & when black wants to play b5. it also leaves the Q-side white squares awfully weak. on the plus side, it prepares the fianchetto--but does black really want to aim the bishop into the teeth of the e-pawn? it seems a little early to decide whether that's its best square--but if black really wants that setup, why not skip c5 & just play 1 ... b6 & 2 ... Bb7?
If I were white I would castle Queenside at that point, so you're white bishop will be aiming at the wrong side for an attack on the king, plus you wasted tempo with b6 when you could have immediately done b5. Sicilian is usually sharp attacks on the king, and in view of black's opening choice, I would say white has the advantage.