What is the benefit of adding yet another profile and not putting it in the ~/Documents/WindowsPowershell directory?  Is this required of a different PS host?

I have lots of goodness in my profile.  I don't want to duplicate, symlink, etc.  I'd rather StudioShell just use the standard profile if possible.

StudioShell should be using your standard profile by default.  Check your settings under Tools>Options>StudioShell and make sure "Load PowerShell Profile Scripts" is checked.  If it is checked and your profile script isn't being loaded, open an issue and let's investigate.

FYI, custom hosts are "supposed" to use their own profile script.  At least that seems to be the custom with other hosts (ISE, PoshConsole, etc).  The reason StudioShell supports the "standard" profile is the reason you mentioned - I want my StudioShell experience to be as close to my PowerShell experience as possible. 

In fact, the only reason StudioShell supports its own profile script is so that you can include IDE-specific session customization when you open StudioShell.  E.g., you can't include this in your standard powershell profile without it raising errors, since the DTE drive is not available:

new-item dte:/commandbars/menubar/tools -name "My Tool" -value { #... }