I recall a similar post a few years ago, and a wise practitioner responded - calculate what the depreciated value would have been by the end of 2021, and use that as the cost of acquisition as at the start of 2022. CRA will accept that value. Alternatively, if you have some way to prove the FMV as of Jan 1, 2022, that would be acceptable.
That applies if it is a class 10 vehicle, but not if it is a class 10.1 vehicle. Also remember that you are just trying to calculate a reasonable FMV to use upon acquisition of the asset, so you could document it either way.
I would question if the half year rule needs to apply since this is the second year the vehicle is on the road. But I guess if you bought a used van from a dealer, the half year rule would definitely apply.