In my experience modeling mostly electrics but also some diesels and a steamer, while the patterns are similar, placement is nearly unique to each class of locomotive. Even for standardized steamers like USRAs there would be a great deal of variance in position. You'd have to make each grab iron a separate mesh (with LODs to turn it off in all but the closest views) and position them, even using rotation for those on the opposite side since exact width of cabs and boilers is different. (And that wouldn't work for those attached at an angle since only rotation, not mirror-imaging, is supported in configs.)
Frankly, I don't think this is a realistic possibility.