You know, this guy's issues aside, one thing that we could write. An Automator (Mac App) like application that can be run with little or no requirements (i.e. boot with not startup) that parses CLI scripts and arranges them within action groups. Again see Automator for examples. But it could be a nice GUI driven script editor.
Things like Add Assign adds a box which lets you enter a name and select a drive using an asl like requestor. Or Execute command which lets you choose where then another drop down shows you all the commands in that directory and allows you to adjust things like stack or env prefs. This would insert all the necessary commands to ensure this environment.
Or how many times have you wanted to assign your system to a sub folder and got tire d of typing things like
assign sys:
assign l: sys:l
assign c: sys:c
assign devs: sys:devs
assign fonts: sys:fonts
....
When we could select a Assign System action and simply enter folder name. The tool would then insert the necessary lines into the script (S:User-Startup or S:Startup-Sequence) as needed.
The actions could be conditional. A lot of potential. I've never had problems with modifying startup scripts but this would still be convenient. Just a thought.