-snip for size-
Jeepers, and here I thought the WH40k universe raped physics hard enough already

Of course, the single biggest hurdle facing the Commander would be on the ground. The Imperium doesn't exactly lack things that can chew up building-sized mechs for breakfast, y'know. Hell, the sheer amount of dakka that a Leman Russ brigade can produce would probably bring it down. There are tanks that are referred to as "titan killers" for a reason. Or if it ran into an actual Titan; THAT would solve the problem quickly.
@ Hans: Refresh my memory, are the Imperators the super-ginormous titans or the smaller ones?