Felixk,
Just about any kite will get you going on smooth pavement as rolling friction is so minimal. The ability to depower is almost essential in my books, especially on bitumen and concrete.

If your kite will fly well, it'll probably also pull you along.
On grass, it depends on so many variables. What sized wheels you are using, tyre pressure, thickness, sponginess or depth of grass and type of ride ie, dirt surfer, mountainboard or carveboard. I would think you'll probably need at least 15 knots with a 5.5 foil, with 8-9 inch wheels on well mowed grass such as a cricket/footy oval.
Good news is I have met a number of people curious about mountain boarding with kites over the last week. If you fly it, they will come!
I think it could get some momentum in Perth over winter. Bring it on I say!
Good winds and thanks for the advice Velocity.