I am fully with you. I think it is a huge step forward to have exchanges which pick up new cryptocurrencies, and the invention of open source software as you say, together with the security gained through cryptographic blockchain networks, can be seen as the basis for allowing this. I can't imagine what potential the cryptocurrency economy would have if exchanges could pick up new cryptocurrencies easily and without fearing damaging actions from rogue altcoin devs. For example:

* Real mining profit from day one
* Possibility to compare different altcoins on their exchange performance from the beginning

So what can be done? One thing would be to better educate people about the ethics of creating a cryptocurrency. As you correctly stated, PREANN would be at the very least appropriate if the dev plans to make blockchain restarts for no reason. But even then: Blockchain restarts should be only an ultimate resort. This becomes clear when thinking about how the blockchains are computed. No matter if it's a CPU, GPU or ASIC coin: People invest computing power into verifying the blocks and computing the hashes. So, even when policies like the hash being used change, it could be considered an environmental crime to just throw away the old data, considering that it doesn't take much development effort to make such changes to a blockchain client without a restart.

But even more can be done, thanks to the blockchain cryptography:

For this, it must be understood that the dev's attack against the old blockchain and its exchanger, miner and user community was very simple: He replaced the software on the advertised seed nodes to be incompatible with the old blockchain, and stopped to distribute the software compatible with the old blockchain.

So, to recover the funds on the exchange, the following steps can be taken:

* Advise people to use the known-to-work software release 0.0.0.1
* Put it on accessible servers and provide their hostnames for people to "addnode" them
* Notify the miners - they will be needed at least to let the difficulty adapt downwards. But they cannot mine on the new blockchain anyway

So, by appropriate usage of the potential of open source and of blockchain networks, it should even be possible to limit the power of rogue devs.

As future steps, I would recommend to make the change to bcrypt from the old blockchain - in a proper way without invalidating blocks. This way, the community NUD and the dictator-dev NUD stay maximally compatible (think CentOS and the product of a certain North American software vendor ). Maybe we can then even convince the dev to join forces. A cryptocurrency with a healthy community is even more valuable after all.