You failed to give any explanation whatsoever of why the existing code base would not be modified to make any needed changes as opposed to doing this swap.
Please answer that question with a detailed explanation.
You also failed to respond to the enormous drop in PAC price leading into this swap. If this swap is so good please explain to me why the coin is being dumped in mass quantity at very devalued prices?
Your answer to what will be done with the existing coins is beyond vague... "probably, "likelyhood" "returned", "burned"...

In other words nobody knows what will be done with the existing coins?
I'm sure there are many reasons why it was decided that the existing blockchain would not be modified. I'm certain that chief amongst those reasons is the fact that old paccoin cannot be traded for bitcoin...100 trillion coin supply is simply too many against bitcoin's 21 million...hence the massive wall at 1-2 sats.
As for my 'vague' reply, I honestly dont think even the devs know what to do with old paccoins. I do know that they cannot profit from them because their fate will be totally transparent to the public.