I'm a hacker, that's how
lol
Actually there is just a straight way - unpack INSTALL.CPK, change text (script/50), repack INSTALL.CPK... I believe almost anyone could do that, as it is really easy.
About that proportional print... Well, this would require quite a lot of time, and anyway you would have to put the end-of-line manually (this is how the script was constructed, I believe there is that #n for next line tag is used), so I am not volunteering into this (I never did that anyway, it is not that hard, but requires good asm knowledge, while I am a mere PSP user)
But just to insert a text to keep things working for fans - you really need proportional in the first place? I thought you do it for fans, and fans would be grateful even for the not perfectly spaced texts, I believe.
"Swap system language" - you mean just swap the buttons and change language when press Home button?