Reconciling those differences is part of the porting process. I do agree that it's a "pipe dream" to expect every single SWF out there will be ported, but it is

Reconciling those differences is part of the porting process. I do agree that it's a "pipe dream" to expect every single SWF out there will be ported, but it is definitely the right way to do it if you're trying to save a SWF. Relying on old binaries of Adobe Flash Player is probably not a good idea from a legal perspective. I'm not a lawyer, and I haven't read the EULA, but I wouldn't be surprised if it didn't allow that type of redistribution. Even if JS+HTML5 dies for some reason in the future, it's not a closed-source proprietary platform like Flash was, so preserving stuff will be much easier.