Getting the Allies really helps when the battle for the gates starts. Not that you'll need it to save your bacon, but they are needed to defend the emperor. Different environments, critters, or even the same critters with different spells would be interesting. The gates just get monotonous. A tip: unless you want tons of daedric hammers and claymores, get the boots of Springheel Jack, the Cowl of Nocturnal, and some potions. Then blitz through the gate towers. In fact, I was able to skip my way past several parts of the Bruma Great Gate simply because I could jump the lava. Yeah, it's kind of cheating, but I just want to have done with those blasted gates.