you can do command line repairs, and yes you can replace "some" files. HOWEVER, some files you "cannot". Unfortunately in 10 years I've never seen any reference stating which can/or cannot, be replaced, although I've certainly done it enough times.
to clarify, if it were an open source application, everything you ask can be done.
Until, and including then, regular backups are the prudent thing to do, especially when you could have countless user configurations lost at any moment.
