I think it's partially a nod to older fans (Hey, look, we're including a toy you had as a kid, updated, because we dig you!), and possibly toy marketing if they even make it of course, but I also think there's an element of the designers on the show liking that design (their own nostalgia for it) and using it... I like the MLC-3, personally, and believe it's a totally plausible design that could've worked as an in-universe thing (some of the mini-rigs, not so much), and so I've incorporated it as a "real" thing, into my little Star Wars world.
The Stormtrooper Transport seems like that to me... It may not even be made a toy at this point. It may also suck given the current state of vehicles in this line, and that this one appears to be a big bigger and better than the original actually. It'll be interesting to see how many NEW vehicle designs they incorporate into this. I didn't get that sense too much from Clone Wars, aside from Clone colors, but that was just as much ROTS as TCW.