Finally got back to this one. I've had a look at the backported datatype and it's not really what I'm after. No matter I'll put together an extension to do what I want.
I'm a little confused at this datatype though. It seems quite complex. What is it meant to do ?
When editing I am able to add multiple "multioptions" then add options to each one of these. When viewed there is of a number of selects (dropdowns) with options specified.