Customize Additional Rows of Keys

The additional row of keys is very nice, but it would be great if you could configure them further for different languages. For example, in Haskell, I have little need for the ';', but a much greater need for ':', so it would make sense if that were the center character. Additionally, it'd be nice to have the ability to add character combinations in those additional keys. To use Haskell again, inserting "->" or "::" with a single keystroke would be very nice.