The 1800s version of the hellopolis, as I see it.
The challenge is this: You exist in a world with all the grand inovations of a society run on steam and exploring even the newest mysteries of electricity... yet wars continue and demand more and more inovations.
As an engineer, it is your job to come up with a means of assaulting high-walled forts on the outskirts of major cities such as New York, Washington DC, Berlin or Richmond. You need a machine that can carry troops through a firefight, a machine to get cannon into position faster than the enemy, and a means of scaling these forts...
solution? Put them all together!
This hellopolis of the civil war is my concept of how a contemporary visionary like Jules Verne would have solved this problem. It trundles accross a shell-hole-pocked field on specially shaped treads supported by a series of strong supports. Above is a large boiler that sits open to the air on the side, with armored walling that sacrifices some safety from bullets to alleviate the intense heat the stokers would otherwise experience. Above that are two floors that are partially open to the air, with cannon forward mounted, which are crewed in the manner of ships guns of the american civil war.
Above that is the ramp that runs to the top of an old-style fort's battlements to allow the troops concealed in the safety rooms on the two floors below to raid the fort from above. and atop this, of course, is the command module and the crank that would drop the iron drawbridge which is cut with an (unshown) rifle slit that allows troops to fire through from the top level at troops on the battlement about to be stormed.
The entire machine is certainly weak to concentrated cannon blasts, but the iron allows it to survive (and often even shrug-off) a number of disorganized shots from even the dreaded 12-pounders.
Although the boiler crew bellow and the 6 cannon crews are open to enemy fire, the bottom leven is heavily reinfirced and contains very thin forward and rear compartments guarded by concrete pillars wrapped in steel that can protect them from heavy response bombardments during the last stage of opperation (while the troops are leaving the upper compartments, and to hide from any concentrated fire or sharp-shooters on the approach, as well.