The Pegasus Hobbies Technobridge is an elegantly designed snap-together plastic kit usable in both modern and futuristic wargames. The packaging boasts that it is over a foot long and they are being quite literal: at its longest it is 12 and 1/8thh inches. The internal width is just under 6.5 inches. Yes, a Baneblade can use it to cross a river or canal, and of course your troops can as well. They could get a cover save from the sides from the 1 inch tall railings. It comes almost ready to use out of the box, snapping together, and cast in a dark grey plastic. I am in the middle of painting mine, but even unpainted it looks pretty good.
If you purchase two of the Technobridges, the central bridge sections could extend the length of the bridge. You would need to use your judgement for how many sections could realistically span the crossing. Each central portion (not the ramp) is 3 inches of more bridge, so you could move up to an 18 inch bridge with another box, leaving two leftover ramp portions. I think it’d still be reasonable if the bridge were 6 or 9 inches longer, but extending it further without modeling further supports might strain the suspension of disbelief. Making the bridge wider would require a good deal of work.
Warmachine players may even be able to make use of it, but traditional swords and sorcery fantasy games or pre-1800s historical gamers will not find much use in it.