First of all congratulations to the Pakistan cricket team for winning the world cup!
Coming back to the point, let us analyze the whole situation rationally.
Assuming that the matches cannot be held in Pakistan at any cost because of safety and security reasons (guess there is no argument contrary to that), we are left with just two possibilities- (1) Share Pakistans share of matches between the remaining hosts or (2) hold it in some neutral venue of PCBs choice.
Looking from PCBs pov, option (1) is ruled out as it doesnt bring any revenue to the country or the board. However, option (2) makes a lot of sense as it is the second best option to having matches in Pakistan. Looking from BCCI and other boards pov, option (1) can create additional revenue while option (2) means no additional revenue; in fact it might lead to losses if the brunt of the new logistics has to borne by these boards. In essence, both sides have valid arguments in their favor.
Solution:
Assuming that there is no animosity or greed involved,
BCCI and ICC should allow Pakistan to hold its share of matches in a neutral venue provided PCB accepts to bear any additional expenses or losses to other boards that might arise due to the new formula. Other boards (apart from the hosts) too must have a say and their preferences too must be taken into account to avoid any clash of interests.