Many kinds of craft need this: VTOL's in hovering mode vs flying mode, spacecraft in flight vs docking mode, rover + skycrane, etc, etc. It'd be nice to be able to switch your control POV before you hit the freaking ground -- and would be nice to have a way to do it from inside a cockpit. Letting us put the 'control from here' option in a control group would let us do both.
It'd also fix the odd rocket that wants to 'control from' undeground for no apparent reason. Just put 'control from here' in stage and it restores on launch and fixes PoV changes that might be caused by a change in stage.