Jim, something like this is certainly doable. I'd prefer to do a stronger version of the 'luminosity modification' we currently do on a mouse over as this leaves us immune to system color changes, different constraint renderings, and the like.. The question becomes how long to keep the highlight? Until the next click outside the shape? Until the next click anywhere?
I could also move the mouse over the shape. This would tell you exactly where it is, but is a little annoying if you select primarily with the mouse, and doesn't work on remote desktops. This behavior could be optional.
I'm also strongly considering adding an 'ORM Diagram Spy' toolwindow that could be used as an alternative to changing the primary selection. This would be a view into an existing diagram, but would not change the current tab selection or diagram position. You would have the option to change either the primary selection, or the 'ORM Diagram Spy' selection. This came up after I added hyperlinks from the verbalization browser (will be in the next drop), which lets you select a column and jump directly to any of the related FactTypes and ObjectTypes. Currently, this changes your selected diagram, but a Diagram Spy window would let you keep your Relational View selection while modifying the underlying ORM model in the diagram spy. Any comments on the plan?