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.
Even within the big-3, the dominance has changed. A decade or two ago, the BCCI, ECB and CA all had equal importance and strength. But once the IPL got established, the BCCI has managed to move ahead and carve a place for itself. Now the other two boards are dependent on the BCCI for a large share of their funds. Even their T20 leagues (Hundred and BBL) attract a lot of revenue from India. When Shashank Manohar was the chairman of the ICC, he took some strong steps to reduce the dominance of the BCCI. But now everything is back to ground zero, ever since the useless businessman Greg Barclay took over.