I guess your idea was ok too though, given mountain board trucks are something people would have. You could make an RC car using one or two of them and take the springs out and put a motor to turn them instead.
That is good because then you only spend money on parts that are also useful for esk8.
You could use the boardnamics AT gear drive for it!
Or you could try to design some full suspension trucks and take the steering and attach it to a servo motor instead of the leaning. That could be useful for riding once reconfigured too.