For something beyond an Editor port like U3 temporarily had, most studios just outsource if they don’t have a dedicated VR team.
U4 having VR support that was developed in-house is unrealistic. SDG working with a team like Escalation Studios is far more probable.
Given the above information, I’m only able to view @Pikzel’s post under the idea that Nelson is outsourcing. I don’t have a problem with Unturned having VR support, but the Unturned II Dev Kit having VR support sounds a bit silly.
It’s more than just a map editor, and I feel like there’s just so many tools that wouldn’t be easily available to you unless the amount of effort put into the U4 Dev Kit is the same as put into the game itself. I don’t think that’s an efficient use of resources, so just focusing on VR support for the game itself would be the main thing, although it’s interesting to think about how U4’s modability would tie into that.
Seems a bit counter-intuitive, but the virtual living room also seems straightforward enough that I don’t have any actual issues with it.
Melee weapons’ hit registration being based on volume sweeps instead of hitscan should make VR support more technically straightforward, although in order to to keep it balanced the damage calculations for VR users would need to keep in mind the amount of force being applied.
Reloading is a similar idea. It should be technically straightforward because of how attachments are separate entities from the gun itself. Mechanically there’d only need to be a VR-specific way to reload (which really just comes down to the game recognizing the action you’re attempting to do). Any reloading-based ability stats would be a bit more difficult to replicate though (i.e., larger mags normally taking longer to reload).
VR support could just come down to the most technically simple implementation, which is just a camera for your head and a way for your handheld VR hardware to work with the game. Mechanically there’s quite a bit of work with stuff like the user interface and maintaining game balance.
The easiest thing would be to make a singleplayer-only port that is developed in partnership with another development studio. Being singleplayer-only, you avoid a lot of the balance concerns by not introducing the player to people that could be more mechanically limited due to using a keyboard/mouse.
Then, the port is either available as a separate game download, or it’s DLC (like you have suggested).