It would be nice if when you are on foot as a passenger or other to be able to walk up to an openable window like HST mk3s or mk1 open the window and press eg Y to windowhang
Unfortunately this is likely to lose support or TOCs Window hanging resulted in several serious injuries, which is why these carriages have been mostly phased out.
DTG did say a a while ago that they will never imploment that feature into the TSW fanchise because of how many times people have been injured and/or killed by doing that. It is possible to do on locomotives but that is for a whole different reason.