"Lock" Widgets together

That would be "grouping", as available in many other applications (most notably vector editing ones). Although this may be useful, I think you should not let "UI guy"s touch an eSpace. Let 'm make the mock-up, or tell you what to move where, but even with locked/grouped items, they can screw the stuff if not careful.

Kilian -

My "UI Guy" has spent DOZENS of hours making changes. He needs to be able to work without my intervention.

J.Ja