Sounds like a wonderful cultural experience!
But you will at least spend half your time in Europe (flying to and from Turkey). You will gain 737NG experience that will be valuable to other carriers (the Gulf carriers will accept it). Like many LCC carriers these days, sounds like an investment in your long-term career if you go to SunExpress.
Question: excluding the potential for Syrian bombs, how would it compare to flying like a slave at Ryanair, Eazy, Vuelling or for Lionair in Asia in terms of gaining "valued" experience??????