ICC has not signed the hosting agreement with PCB, so PCB has no legal document with it to pursue any cause.
If PCB threatens to boycott the CT 2025, SL is likely to take its place. PCB will end up losing the hosting rights plus the ICC revenue share and spoil relations with the ICC.
There are only three scenarios here
ICC agrees to host the tournament in Pakistan without India and all members agree to take a 500mn USD loss.
ICC moves the tournament out of Pakistan wholly or partially and compensates Pakistan with a few million dollars.
PCB agrees to make up the losses for ICC and the tournament goes ahead in Pakistan without India.
If the tournament isn't financially viable, ICC will have no option but to move the tournament.
I would employ a firmer and harsher strategy this time around citing Pakistan's participation in India recently. Your suggested solution is valid but acquiring funds is unrealistic.
Before anything happens, I would wait to see what the ICC does about the hosting agreement. It is due in the next month or so, which should be allowed to play out and I would not negotiate during that period with anyone. Continue to say we wish to host the tournament and that's it. No need to give the ICC outs.
We have to remember the ICC also has a separate agreement for its members and this contract will come with a due process for removing a host after the bidding/selection has been completed.
I would exercise this right as PCB.
The ICC must produce a justifiable reason for removing the tournament from Pakistan
(i.e. security, team suspension like SL recently). The members will eventually have a vote on this matter with a written reason for why this decision is being made. We all know the reason will be India's non-participation and damage to profits.
The PCB can obviously attempt to garner votes but it's unlikely to get enough members on its side.
Once this removal goes through, the PCB should refuse to play India in all upcoming ICC tournaments minus knockout rounds. No need to boycott an entire tournament. This ensures the PCB receives payment for its participation and does not need to recognize India's presence at the Champions Trophy. If the ICC attempts to schedule a group game against India, the PCB should forfeit it. There are no set consequences for forfeiting matches in ICC rules minus the loss of tournament points.
This will make an appropriate and strong point against the BCCI and ICC's actions.
The PCB has to be honest with itself and note it's getting tossed around by the BCCI and its puppet. Once it gets to that, you should be brave and take it head-on every step of the way.
It will take a courageous PCB to do this but they need to stick to their guns. They need to stand up for themselves because their reasoning is airtight this time around.
It's unfortunate the BCCI/India is doing things like this and mish-mashing politics with sport. The courteous nature of Indian fans towards the Pakistan team showed the BCCI is not a good representation of its fans. They disrespect their fans
(World Cup ticket issues), they disrespect ICC members
(IPL scheduling, Asia Cup reserve day), they disrespect the ICC, and of course they disrespect Pakistan.