How about having the feature so that when youre browsing two websites, you can actually browse them at the same time in the same window. For example, you have one window open with only one tab open, if you click a button called, say '50/50', it'll split that tab vertically into two seperate browsing pages so that you can view two pages at a time within just the one tab. Obviously both having their own scroll bars.
That would be a funky feature. The only problem there though is the webpages having to fit / squeeze into a smaller window. It might require some websites to have horizontal scrolls which annoys me. Although on this widescreen laptop I'm using it wouldn't really be a problem.