It is annoying to have the cursor on a blank line slam left when the file is saved while its still open.
If I remember correctly VisualStudio has a nice (if complicated to implement) solution, it never saved the superfluous whitespaces, but graphically, in the editor it appeared to leave them alone so it didn't cause you to re-indent while editing after a save.
Maybe that could be easily implemented by simply not changing the buffer on save, sure it leaves the spaces on the ends of the lines in the buffer too, but they get stripped again on the next save so it doesn't matter. If you really want to strip them in the buffer you should use the menu item rather than (ab)using save.
It doesn't keep the indents after close, but that seems a reasonable compromise for a simple change.
Cheers Lex