To put a unit like that in you would have to have some major airport missions. If someone were to make a submod containing these units they should also make some new airport missions and maybe a new airport freeplay.
The point to the game is to save people, so the best way is a way that doesn't involve anyone getting hurt. Well with v2.0 you can't use ambulances for dead people.
By way of comparison, here is the one it's replacing: http://www.emergencyrigs.net/viewphoto.asp?PhotoID=205 http://www.emergencyrigs.net/viewphoto.asp?PhotoID=206 It's a 1989 water tanker.