If I remember from seeing WWRY in London, the Dominion has a huge proscenium, so it's probably an asset that the others don't have. And the theatre itself is pretty bare in terms of design, so they wouldn't have a problem designing the house however they want. And sightlines I think are good there.
As for splitting it up...I think it's not to crazy an idea. It worked for His Dark Materials in London, and it sold out in both runs. And I think the Brits might actually be more up for LOTR more than Wicked!
"Hey little girls, look at all the men in shiny shirts and no wives!" - Jackie Hoffman, Xanadu, 19 Feb 2008