VR, reflective surfaces, etc leading also to engine consideration

A few ideas building on existing codebase

VR support - basic - 3d cabs
VR support - advanced - e.g. grabbable controls (VR equivalent of "touch controls" in existing codebase)
Reflective surfaces e.g. mirrors (platform mirrors / train mirrors - single person operation)
Live feed camera monitors (i.e. display feed from camera placed in world)
Train stops / trips (would welcome references if already achievable through plugins)

Otherwise (and this might deserve a separate topic) - I've seen other mention of alternate graphics or dare I say 'game' engines. This seems quite an interesting angle, especially in areas such as dynamic weather, improved lighting, general graphical fidelity, and maybe even physics simulation (i.e. possibly utilize elements of an existing physics implementation rather than coding explicitly). I briefly played around a bit with Unity and could (partially) load and display a route using some ported code (RouteParser, B3dCsvObjectParser etc), but endless devil in the detail to do anything serious.
Furthermore, the idea of coupling to a commercial graphics/game (e.g. Unity or even Unreal despite being a bit more 'open' AFAIK) also seems dangerous/wrong for an open project.
I wonder if there are any other comparable open source simulations/games that have successfully pursued ambitions for improved atmospheric graphics and simulation elements whilst balancing the openness of underlying dependencies. I think Blender has a built-in game engine but I'm not sure how well supported it is these days.