It should analyze permissions errors, etc. and repair them, requiring sudo after instantiation if required.
Some brew doctor warnings may be able to direct the user to this tool.
A log should be made, so if it doesn't work, we can figure out why.
That sounds great.
For the permissions part at least, Homebrew could come in an installer package that leaves a bom receipt so that diskutil repairPermissions could do the repairing: http://support.apple.com/kb/HT1452
Great idea; but closing due to lack of action. Any specific things we want to do should be made into pull requests.