Perhaps an updated Royal Train addon (YES, I _know_ the Royal Train apparently will not play any part in the Queen's casket being transported home to England)? Or a "Princess Elizabeth" Princess Royal class?
Nothing planned right now but there is this from a while back: https://store.steampowered.com/app/208284/Train_Simulator_Class_67_Diamond_Jubilee_Loco_AddOn/ Would personally love to see a Princess Royal Class myself. Best, Steve