I play GTA in 1st person, switching back to 3rd occasionally just to admire the scene.
I don't see that 3rd person adds any combat advantage - quite the opposite in fact.
There's in-game controls - movement, actions etc. - and there's UI controls, that interface the real and virtual worlds.
Because it is a virtual world, operated from the real one, this interface is insurmountable, at least via current techs. The interface can't be thwarted, it has to be exploited. You can't beat it, so join it.
External view is an interface control. It is a misapprehension to conflate it with the in-game controls. It's no more "unrealistic" or "un-immersive" than a game options menu. It no more "breaks the fourth wall" than a pause button or "load new commander?" profile selection; you simply can't apply measures of gameworld consistency to the UI, it's like confusing hardware with software...
And if it's observational advantages of the increased FOV that worries you, then there's no reason why the FOV has to increase for external view anyway (though it'd be a lame restriction if FOV isn't fully adjustable - fisheye galore if you can deal with it), and besides, in that case you ought to be far more worried about other players having much larger fields than you... my 6-screen rig allows really wide FoV's, and VR headsets will have even wider ones...
I always switch to external view when landing or launching in Pioneer because mentally i'm thinking "wow, that's me in that ship on that launchpad, in that city" etc. etc. It's a real immersion booster IMHO...