Remove index from subpage path with mod_rewrite?

[yojoe]

I tested that in the .htaccess but the links to subpages in the submenu were not modified, so calling these subpages the URLs still contained /index/ and by that I ran into an error

Rewrite works as supposed, and redirects user where he should be redirected.
Rewrite doesn't interfere into script's code. It may work along with it (passing some variables), but it does not override script's output text. You have to change it manually according to what you want to achieve.
But then rewrite rules wouldn't be needed.