Although I understand your reasoning to keep the "Highlight" button in the VP window, it's not consistent with a UI philosphy, where all the settings should be in one place. Perhaps the happy compromise is to make it so that getting to the terrain settings is easier from the Settings button? (If it could be done, no setting should be more than two clicks away. I propose that that the "Inst Group" button be repurposed. Does anyone change the grouping once they've customized it the way they like?)
On the split screen: I figure it's coming anyway, so I didn't say anything about it, as it would make my mock up moot.
I'm not a fan of split screen, at least not for long term use in flight. The reason I bought a 9 inch 3:2 hi-res tablet was to see as much as the map around me as possible. (We move at about 3 miles a minute and I like looking far ahead.) A split screen for the VP window defeats the goal I'm trying to accomplish here (trimming down the window) to present additional information without taking away from my view of the map.
But I'd bet split screen is coming, so you'll be able to set up iFly any way you like it.