Here you are right Big-3 is main problem in ICC and cricket's better future specially Indian are doing dirty politics after introduction of IPL and having huge funds in their pockets.
But here concern is not IPL, and we are not talking why they are not allowing their players for other leagues and now allowing Pakistani cricketers in their league here is concern these all boards need to do some worth with ICC for having better structure and other facilities in countries where we can do some good for this game and youths can join this as professional cricketer which is increase its popularity, and we will be able to have some more good and quality teams in this frame.
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.
I think you are missing some important things here. pakistan players are not allowed to play in IPL because of the political situation between both the two countries. As far as i know , the pakistan board will also not allow players to play in IPL.
And why would BBL ban West Indies ? They will never ban them as every league wants good international players to come and play the league. If leagues start banning international players, no one will be willing to watch tournaments with national players only.