I think all boards have accepted the dominance of big 3 specially India. No board is not willing to lose his IPL share thats why no one is speaking against BCCI policies.
IPL aside, I do agree with you that all boards less big 3 must unite together to make icc powerful entity to safe guard there rights otherwise today Pakistani players are not in IPL, tomorrow BBL may ban WI players or so on. Only in presence of strong ICC, rights of small entities will be protected.
Your statement is completely wrong because it's not ICC duty to check in these leagues and try interference, it's all about every country and board's own decision who is coming and who is not coming. Right now if ICC can do then they need to settle things for better adoption and marketing which is very important and most chances in next few years we are going to have completely changed set up in this game of cricket.
I guess this is going to work like soccer just very few events under ICC and all other enjoying their own leagues which is very good and fair for all because this will bring some better and strong system which helps these countries for having good funds for their domestic setup but sadly too many countries will be out of this all, and they will lose their all domestic system because they can't afford these leagues.