My friend did something like this, only his hills are taller.
I saw one unexpected result, even on my little hills. Players are avoiding higher hexes. I think miniature is more exposed not only in a game mechanic, but physically, too. They are hidden "better" behind 3d hill and they're safer from units in front of them, since the players sometimes overestimate partial cover. :) Remember that in your games, it really gives an advantage.
