Actually this effectively solves the "parked on mobs" issue. Either side can now shoot your vehicle if you use the vehicle in a non-intended way to cause others trouble (by parking on a mob so they cannot loot it.) Seems to me that "all vehicles are subject to damage by other players." solves that neatly.
The only argument I could see for this being a "bad change" comes from a position where the player believes that they are intended to be able to play the game completely PvE without ever interacting with other players in a PvP mode. I believe a core design premise of this game is a lack of safety and an air of tension in the wild places, and as such, this change seems to support that intent.
As an aside, without a Dev's call on whether or not Neocron is intended to be played "alone/together" (like WoW/CoH/EQ etc.) or whether Neocron is intended to be a community game that cannot be soloed safely in it's entirety, it's hard to know where the focus should be with regard to changes.