I am sorry - but changing players won't change anything. We will be able to play one or two competitive tests every once in a while but that's about it - nothing more. It is not one or two player we have a problem with in the test format - the problem is with the whole lot. Tell me one single cricketer in the team that has test mentality. Tell me one batsman who is even remotely capable of saving a test match. Who is our current best test batsman? Tamim. Now that kind of Sehwagesque approach might look pleasant for the eye but rarely achieves anything significant, especially for a team like Bangladesh. Sehwag's style often works with India because they usually go for the win, which often requires scoring runs quickly. Also, when he fails, he has people like Dravid, Laxman, and Tendulkar to fall back to. But for Bangladesh, we are yet to achieve a fighting draw since we got test status. We need people who will grind it out there. Hanif Mohammad should be our idol, not Sehwag.
Now this type of test mentality cannot be just taught. No coach in the world can teach our batsman to play in a test mode. It is something that players learn after playing first class cricket for years, sometimes even before when playing test cricket. Remember, how Tendulkar came into the spotlight? It was his huge partnership with Vinod Kambli at school level that made him famous. Again, that innings was applauded for its duration and length, not explosiveness.
Look at our players. Let alone school cricket, how many of our batsmen have scored a double century or even a 150+ at first class level? If our batsmen do not have the mindset to play long innings when the bowling attacks of our FC teams are ordinary and the tracks are flat and batting-friendly, how can we expect them to compete in test matches against quality attack?
To summarize, my main point is that changing players will be only treating the symptom. Unless and until we treat the "cause", we will be a "fledgling" test nation forever.