I think that the idea of having the more 'diluted' talent pool early in the season and then switching to the more elite comp later isn't actually a bad thing. As long as the competitions are played hard, not picnic cricket, then this gives the young guys a chance to impress early and then the top performers a chance to face off against each other later. If you make it too hard for guys to make a career of the sport then they will end up giving up the game so the chances of having late blooming players (eg Mike Hussey and Ed Cowan for Australia) is almost impossible.
Before I referred to Ayub and Mehrab as young, by Bangladesh standards it's true that they are considered senior players. The fact is they are young and batsmen sometimes don't fully blossom until they are about 30. You need to keep these guys in the sport because they are going to improve more and more and need a chance to keep performing, not be pushed out by the next young prodigy. On the other hand the prodigies also need a chance to play so you need enough playing spots out there.