Eckard,
Not emission theory. And the scenario meets all observations and findings WITHOUT having to invoke influence into the future. The emitter may indeed also be moving, but was at a point in space 1 lyr away when emitting the photons/wave or whatever you prefer, which then takes 1 lyr to reach you. Lets be realistic and call it a wavefront light pulse constituted by many 'photons.'
Vince's velocity DOES of course matter because the whole problem is ALL about relative velocities. (You seem to have conveniently forgotten that fact for your own proposition).
Let us then consider that your friend Vince is the only one in motion, moving at v towards the source, but is LEVEL with you when the wavefront arrives. Now you and your 7 friends all do the calculation and find that the photons are propagating at c wrt yourselves.
But when Vince also detects the photons, and also does the calculation and finds them moving at c wrt HIM then you would call him a fool and have no logical explanation (nor does SR!)
In fact only one LOGICAL explanation can exist. It is that the photone which YOU detected were indeed doing relative c+v wrt Vince. Which means that the photons HE detected were also approaching him at relative c+v. It is then the calculation which assumes the wrong mathematical formula, because it ignores the fact that the photons we 'measure' have ALREADY interacted with our detectors, which we know from optical science to be true anyway!
The datum for defining c simply changes to the new inertial system rest frame.
I suggest that is logically irrefutable. (DFM). Happy a good new years eve.
Peter