Thanks.
And I need to ask for more info - sym links are beyond my current understanding.
My reason for wanting it this way is flexibility and control. I always keep the root as clear as possible, with a specific directory into which I install all apps - even though they may 'publish' into the root.
That's where I appreciate the functionality to specify an url for the install and a different one for the publishing path. So yeah, that's a feature request for a future upgrade.
Meantime though, I'm happy to edit core files and/or htaccess to get it working - but need to be told just what to do.