Definitely a +1 on this idea.
While the permissions checker is a good tool, it could be improved greatly with just one change:
Right now, all it tells you is that the permissions are "high enough", or "not high enough".
Much better would be an addition to tell you what they actually should *BE*, especially on servers that don't use PHPsuexec (where almost everything can be 755/644).
e.g. If 755 permissions are all that's required, and the directory is presently 777, have that be flagged green as before, but with (755) shown as a suggestion next to it. If it's 755, but actually needs 777, flag it red as before with (755) shown.
Same with files, and minimums. I use 444 for a couple things, 644 for others, some at 777, etc.