So I'm doing like 100 mph in an ice 3 on sandpatch and I flew off a mountain side, awesome but I don't want it to just cut to a black screen,I want to continue to see me flying off the mountain even if the physics are bad to get a good laugh at that (in on ps4)
I get the sentiment, but when you really think about it, it's good for one or two laughs and after that it's just a LOT of work for no real gain and wasted ressources.
Also your most likely find that the train owners that let Dovetail put these these trains in game don't want their respective trains being crashed or derailed for poo's and giggles, plus it was stated by Sam in a thread in the xbox forum that they will let crash but won't glorify it so it fades to black screen, to keep with the family friendly nature of the game and company.
Same reason the trucks in ATS/ETS have no visible damage. Licencers don't like that. Though you can put them on their sides.
Then there are games out there the use fictional cars that can be used in this way, like racing games car company's don't like that with there Licence cars, so why not have some fictional trains and are TSW concepts something a bit different can be a good thing, if its done right, and just for fun it can look just like another train, but not, its like its own concept fictional train that can only be used in the scenario planner where you can have rules set to off for them trains only and not the Licence trains...
Dovetail are never going to do anything like what you want, it goes against the family friendly nature that the company prides itself on, as said before wrong game, the crash physics in this game are all your ever going to get FULL STOP.