I dont know if it could be done via an addon, though it would be nice.
You would need to be able to be a stationary soveriegn point (like an aircraft) but without the plane, 'and' be able to get out of your plane.
This is for unlimited distances, not just for say 20 feet away.
An example. Lets say someone is making a tank simulator and some tank models, and they are training soldiers in it. Lets say the tank goes out of service but one ahead is unmanned, about 200 feet away, so they deplane the tank (hop out) and run (optional over walking) and get to the other tank, click 'enter' and voila, they are in the VC setting point. Click control / E and start up the tank and continue.
This would also mean that you would be able to park planes 'in' sim by just getting out of one. For that game save, your plane would be 'there'. So if you landed in the forest (helo or tank or something, and got out, went to a cliff edge, saved at that point, your plane would need to be there when you went back to that save, so the sim would need to be able to park planes in the landscape.
Also, it would be nice if you could be standing on the tarmac and bring up a set of planes and 'save'. Here is a 'for instance.
You have a hanger of elaborate fighter aircraft, but none are in the hanger. You have the hanger scenery, no planes in it. You would need to go about doing elaborate parking spots for the planes in a airport setup program, also a AI setup program to have planes that have flight plans to park there.
BUT....!!! With this system (walk around) you could 'stand' at a spot, click Select Aircraft, and choose a plane, Bing, you are in the plane, its facing where you were, and it locates its VC at the point you were standing at. Then you get out, walk to another point, select Aircraft again, bring up a different plane (C-130 for instance), it appears, you are in it, get out, walk to another point, repeat, and when you are done, hit Save Flight and call it something like 'My Hanger Selection 01'. Now, the next time you boot up that flight, your choice of 5 planes are there. You pick what you want, walk around, pre flight it, get in, taxi out, fly your brains out, land, etc.
It would be great also for payware planes as you could have 5 different paint schemes or armament loadouts to select from, walk up to it, get in, fly.
It might also be cool for P3D Build 2.0 as you could have your main stock planes at some hanger base, and be able to chose one from them. A default (perhaps) new way of choosing planes, which is totally realistic. You do the same at a real airport. You look out on the field and see the planes and you get in your assigned plane.
It would be pretty cool....