Just a note on "this is already modeled" things like Object 195 and the other old vehicle models that got leaked ages ago (there was Object 172M-2 IIRC, XM723 etc.)
These vehicles have generally bad models and have to be overhauled from scratch, which is pretty much like making a new model from scratch. Their chance of appearance is therefore the same as for any other vehicle. Sometimes actually lower, because they already got leaked and the surprise was therefore kinda spoiled (we have like 10 such models that we are certain will not appear in 2020/2021 for example, IIRC all 2021 vehicles will be new). In some cases, using older models as a basis does represent some savings but more often it does not.