Thanks for the replies, they all bring up valid points, and I get that Password Safe isn't/might not be willing/able to change in this regard. I haven't looked at the source, but I imagine making a change like this could mean the whole thing would need to be rewritten. Certainly there are workarounds, but they have their downsides. The fundamental problem is that Password Safe's biggest weakness isn't its algorithm or anything else, it's someone in a position of power asking/telling someone to open...
I don't think I'm being paranoid when I say that the possibility of being asked by customs officials to open my safe for them is getting more and more likely. I want to be able to put in an alternate password in this situation, that opens an alternate safe that can have some curated content in there. It needs to all be included in the same pwsafe file. That way I've given them what they want and they can't prove that I haven't. It legitimizes why I have the program and saves me having to delete pwsafe...