The AT-XT is one of my favourite Star Wars designs, and has been since I played the original Clone Wars game a good 15 or so years ago. It's a walker that hasn't gotten a whole lot of attention Lego wise, and the only MOCs I could find were typically larger than minifig scale. There aren't a whole lot of sources to go off either. The curved design of it is difficult to recreate at minifig scale in Lego, however I came up with something I'm quite happy with in LDD.
This is Wookieepedia's image of the AT-XT, and my primary reference.
Front of the walker, a single Clone Trooper in the cockpit. He barely fits, and is not easily removable. The top mounted mortars and chin mounted blasters have a small amount of articulation, being able to pivot up and down slightly. The head was originally designed to be able to swivel, however it was locked in place by a plate on the back. Removing the back plate would allow for the head to swivel again, but I'm not sure if the in-universe one actually could. The pictured, curved cockpit is not particularly accurate, however I really like how sleek it is and how well it blends with the rest of the body shape.
Higher up view of the walker.
Side/rear view, looking again at various sources I feel that the mortar top section should be a little longer.
Top/rear view, I was a little unsure how to tackle the mortar section and as is it is a lot less curvy than it should be.
All of the joints are articulated, the leg joints are all click hinges while the hip joints are just bars. I suspect such a connection would not hold up well when built with real bricks, but I couldn't find a suitable alternative at the time I designed it.
Another angle of the walker in motion. I'm not a fan of how flat the feet are, but I couldn't come up with a more 3D design that I liked more at this scale. All of the solutions I could come up with are larger than this scale.
I also whipped up this alternative cockpit cover. It's a lot more accurate to the in-universe design, however I personally prefer the single piece windshield for its sleekness. The 1x1 round plates that were also added in this picture would be a nice place for the Republic emblem tile.
This is my favourite alternate foot design, it looks far better than the flat feet above but this design too large.
Rear view with the large foot design, the feet shouldn't be that close together, especially at the rear toes.
I actually finished up these versions of the model back in late 2016, and haven't touched them since so there may have been new parts released that might help.
While I would love to build this with real bricks, there are three notable flaws holding me back. For one, the 2x2 wedge plate does not exist in dark red, and those add a significant portion of the dark red highlighting on the head. Secondly, I'm highly dubious of how well the hip joints would hold up with the weight of the head, and I suspect it would crumple quite quickly without a significant redesign. A stand would of course make things easier but I'd much rather it be able to stand on its own. Finally, I'm undecided on the feet. The to-scale feet are flat and not particularly well shaped, but the more accurate looking feet are much larger than they should be.
Something else I would also like to change before building this with real bricks is the top mortar block. After another look at various sources I feel it should be a little longer, and I'm not too happy with the shaping on it, it should be a lot more curvy and smooth.
I hope you enjoyed this creation, any comments, criticisms and suggestions would be appreciated. I'm also happy to send the .lxf files if you would like to have a tinker.
A link to my original Flickr album can be found here: (link)