I added the following. If you want to revise this and compress it, that's fine. And I have no clue about any of the formatting techniques on the wiki, so if you'd like to rework some of the keywords into links to other pages, that'd be great, since I have no idea how to do so.
Further evidence supporting the theory that Fright Train is the Bunker: Engine of War is his height. In the initial Vengeance art, Fright Train can be seen standing significantly taller than Baron Blade, who is 5' 11''. In Bunker's bio, it is said that the Bunker suit is stands 9' 11'', so we can assume that is the general height of the suits. In the Freedom Six description, it says that the Bunker suit currently used is hollowed out, meaning the person wearing the suit would have to stand almost as tall as the suit itself. Given that Fright Train stands so much taller than Baron Blade, this suggests that Fright Train would be the only person large enough to wear an empty Bunker suit.