Railjacks can move at 200m/s Unmodded and up to 700m/s so i have no idea why you would even want to use it in there because it will just be you hitting invisible walls every time you try to move because of how fast Railjacks are. Even in the biggest open world (Orb vallis at 8.2km square) you will be able to clear it in less then 10 seconds. all that would achieve is make open worlds feel claustrophobic because of how big Railjacks are and how fast they move. I get that DE showed a cut-scene of it and people thought they would be able to do it, but i don't remember ever it being promised. Also ground to space is one of the most expensive and difficult things to achieve in gaming, go ask Star Citizen Devs, it will take millions of dollars and years just to modify a game Engine like Unreal or Evolution to support 64bit world space coordinates to make it feasible.
