Hi Michael,

>...left clicking would always be for hide/show.
>So whether you see an eye or a lock, if you left-click on it, it would blank out and be hidden.
>If it was blank, then doing a left-click will show it and make an eye or a lock appear.

This would be quite direct and clean.

About locking, it can be interesting to have two different types of locking, layers and objects.
Since the objects are automatically highlited when we move the mouse over them or their parts,
a script step could allow locking with a keypress on "mouse over".

Moving objects between layers
I just thought I'd mention something I quite like in Blender :
When the user wants to move an object to another layer,
he presses the "M" key,
a pop-up layer grid appears,
and the user clicks on the destination layer (if the destination layer is hidden, the object disappears).

Please feel free to mention if all this "outsider thinking" becomes annoying
(if it seems to bring you back in too basic things).

- Michel