-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?
Imperators are the biggest Imperial titans. They have a massive battle-cathedral on their backs that has spires of guns and such on it that are the size of Warhound Scout Titans. It takes several Legios of smaller Titans to kill one.
Yeah, I'd have to go with the Titan in that case. I'm guessing that much firepower would be enough to vaporize Tokyo-3 without breaking a sweat. It all depends on if the AT-field decides to work or not, and how powerful it decides to be for that episode.
Now, a smaller titan, like maybe a Warhound...that I can see an Eva taking on reasonably well.
IIRC, an EVA and pilot could theoretically stop
anything with their AT field, assuming sufficient strength of will. Given the sort of shit the Angels pulled with it, it would be absolutely terrifying if weaponized in a reliable form. Hell, you could probably make shipkillers that are essentially just a fighter with the proper sort of pilot forming an AT field wedge in front of it.
Let's go back to the whole "cloning the God-Emperor of Mankind" idea for a moment. Take Star Wars cloning tech: I think we've got sufficient evidence to conclude that it functions perfectly insofar as that it creates exact genetic duplicates of the original donor, but the issue is whether it would also function in such a way as to transfer the GEoM's pskyer ability/status as a living god to the clones. If so, any Imperium v. Empire scenario would end pretty much the moment a reasonably sound of mind Imperial got their hands on SW cloning tech and... Okay, it would be game over after several months/years/decades of travel, when it got back to Terra. I think the thought process there could probably follow this pattern:
[Assumption]: Cloning duplicates the body.
[Knowledge]: GEoM's body is failing, soul is intact.
[Knowledge]: GEoM is, as indicated by the name, a god.
[Assumption]: ∴ if a duplicate of the body of the GEoM were to exist, he could transfer himself to it.
(Note that this may take the form of the 'pull the plug' scenario with that splinter section that wants to go through with it.)
Once they clone the GEoM, assuming his status as a god is preserved, everything is irrelevant. You've got a GEoM with no experience (given that the Jango clones had to be taught everything during their development cycle rather than inheriting his knowledge), who will be raised by the bloody (in more than one sense, hah) Imperium. Best case scenario for everyone involved is that his natural talents and intelligence guide the clone onto the same path as his "father".
The worst-case scenario is that you have a God-Emperor of Mankind who completely buys into the superstitions and pathological hatreds of the Imperium, with the ability to clone himself endlessly. Every enemy of the Imperium would be overrun by a virtual tide of power-armored God-Emperor clones. It would turn the Imperium into the gorram 'Nids!
Imperium versus Empire would be over in a matter of weeks anyway, because the LARGEST SW ships are ALMOST but not quite the size of Imperium Cruisers. Of which there are very, very many. Unless you give the Empire all their superweapons. Then it gets more interesting. Then again, we also have to consider the fact that Empire FTL is way fucking faster, way more efficient, way more reliable, and way less likely to get your ass eaten by psychic manifestations of jealous and anger. So, the Empire could fight a very effective guerilla campaign against the Imperium.
Oh my god, the Empire would become the Rebels. Except with superweapons around their few stronghold worlds.
The FTL has always been the big advantage for the Empire in Empire v. Imperium fights, and a proper Imperium fleet would curbstomp just about anything the Empire could bring to bear. Hence why most of the crossovers pit an Imperial fleet against a hodgepodge of poorly commanded/Rogue Trader ships. If the Empire was aware of what they were up against and got a hyper-capable planetkiller like the Death Star into the 40K galaxy, they could pop into Sol and crack Terra open before the Imperium even got news of first contact.
On the flipside, the Empire would never be able to hold territory against the Imperium, just raid and run around behind the lines capturing... DEAR GOD, THE IMPERIALS ARE PLANETSIDE 2 PLAYERS.