I think a split would be an extremely poor result for international cricket, especially since we are at at time where Test cricket is most wide open. By forcing a split, you are asking the ICC to do exactly what you have presumably accused the BCCI of doing--killing Test cricket. Test cricket is only going to thrive if there is competition and right now the top 4 in the world could make a strong claim for #1.
And as for your query, India would be backed by the BCB and SLC at the very least. The BCCI helps out a lot of boards financially, both directly and indirectly. I think the PCB would be turned as well, given the money to be made from potential India-Pakistan encounters. In fact, I think you'd only be looking at Australia, South Africa, England and New Zealand sticking together, and even then I'm not sure those nations would back a split. Cricket Australia, in particular, has pushed for the 7-match ODI series agreement with India, which shows how much they value the match-up, financially.