I think that the response to both posts could be a script that you set as screensaver, and that can do all you mentioned.
You can copy powerdimmer's executable twice, each one with different options (for day and night), and the script would run each of them.
As for powerdimmer not recognizing keyboard events, it has never happened to me...
Having 2 different screensavers is quite easy if you have a script that controls them, it would activate powerdimmer first, then send a key for powerdimmer to be closed, and would then launch the other screensaver.
Just my 0,02$..