Repair is a very optimistic option. It fails quite often. Not in a way that makes you more vulnerable, just the repair will fail outright, or the file left after repair will be corrupt/unstable.

Delete is not the safe option, quite the contrary, it should be the last thing you try. As you are aware by what you posted, legitimate system files (like svchost) can be infected, and deleting them can make thing go from bad to worse. For this reason Quarantine is usually the recommended first option. Once it is isolated in the virus chest, it is cut off from your system, but is recoverable even from safe mode, in case its removal causes problems (this is also a good countermeasure against false positives). Delete is very final, and thus so is any damage it could cause.
An oft-reffered to About.com article on this>>http://antivirus.about.com/b/2007/03/11/clean-quarantine-or-delete.htm

Automated action where removed from Boot Scan for a users own safety, as it is a very powerful function, and each detection really should be reviewed before an action is taken. A major PITA as a boot-scan is so long, but it is for users own safety first.

The wishlist was recently taken down (bloated beyond repair), but plans for a replacement are in motion. Avast! does value user input, they are just between submission systems for ideas at the moment.