It will help. Think of it this way, there are atleast 6 world-class coaches and atleast 30 international in-form players who will be playing with our young players. That will help the young players toughen up their mindset to play at the international stage.
Will it hamper our first class cricket? No. We can argue till the cows come home but the fact of the matter is, only INDIA is the country that seems ( on surface) that is impacted by IPL. But people are not acknowledging that Indians are not playing their T20 leading scorers in Test are they? Did they have better bowlers before the IPL and now lost them? No... Are the South Africans, Australians or Pakistanis affected by T20, while dominating Test Cricket? No
So to prove that T20 impacted First Class is total bull because India has one of the most gruelling FC cricket in the world still and the strongest T20 infrastructure yet they are suffering at Test is due to their Star worshipping, poor planning and seleciton process. Previous T20 world champion Pakistan's BOOM BOOM cricket is also co-existing with players who are dominating test cricket; No need to mention Australia's position here..
The reality is without T20 tournament, Bangladeshi players were not in a position to compete in that format and gain the exposure they need for a new world of cricket. We needed a new revenue stream for our players and board to take the sport professionally and be in-form and compete internationally. The rest is upto BCB think-tank on how to re-invest the money into building new training facilities, hire quality staff or build strong A team, U-13, U-17, U19 teams..