The Classic Dearnought wouldn't be that hard to articulate. Give that they are really just a big machine you don't have to worry about hiding joints, although some changes might have to be made unless they want to go crazy with the articulation. heres a shitty little diagram I made if I was asked to creat articulation in a standard Mk V Dreadnought.
The Main body wouldn't need to be anthing more than a big chunky piece of plastic. The arms just plug into the body and would just be simple swivels that let it rotate. Some kind of butterfly joint could be used but I given the chunky nature I don't think it could be done well.
From there the minimal effot for the arms would be single jointed elbows with a "bicept" swivel but only on arms that actually have, well arms, if its just like an assault cannon or a plasma gun plugged into the upper arm it wouldn't need to be articulated. For the actual arm put the section with the fingers on a dumbell joint so it can rotate around. If able we add some finger articulation for grabbing stuff.
For the lower half the crotch area also just pulgs into the upper like most figures and we get a simple waist rotation from it. Now we get to the part where changes to the design might come in.
Because of the wide stance the Dreadnoughts take simple straight forward and back isn't doable unless we just straighten them out like how the Redemptor does. Then its just simple swivel at the upper leg, some single jointed knees and dumbells for the feel with possible toe articulation.
If we can't to maintain the wide stance we will need a more complicated system at the waist/crotch are for articulation. Very doable, probably just more expensive.
So a Classic Dreadnought is ver much doable, it just wouldn't be super articulated, but then I never really thought or assumed Dreadnought were supposed to or required to be very dexterous.