Given our precarious position at the 5, giving up Semih for Parker is too much for too little in return. I don't think we should trade him, but if we go that route, we can get more for him than Parker.
Houston is desperate for a serviceable big man with upside and could be a good trading partner for us. I'm sure Semih + Bradley, who is equivalent to decent first round draft pick + filler could get us one of C.Lee, TWill or Battier (who could turn out to be just a rental for us). The latter two are preferable given their ability to play the 3, but I'd take Lee in that scenario, and try to get the 3 somewhere else.