Is the job done?
I mean, wether the person looks like working or not should not be relevant. Performance should be relevant. If that worker makes more stuff than others, where is the problem?
This person works another way than the average. Is probably not able to stay focused as much as its colleagues. Is able to make the job anyways. Well, then it's time to use that person the way it works. Not all workers are similar. Some need a lot of sweat to get things done. Others need a lot of pause time to get things done.
That being said, there i one situation in which those people can be a problem : it's when jealousy arises, and the whole team spirit falls down. It does not happen often, to my experience, but it may happen. In this case, strict measures shall be taken. But in other cases, why do you want to get rid of someone more productive than his colleagues?
EDIT : from your Edit, I understand that you've got 2 objectives :
- Keep the other workers working and not looking at him
- Prevent him from surprising behaviours that may provoke dangerous delays in your operations.
Point 2 is especially important, and changes somewhat my point of view on the topic. It means he cannot work as others do. You don't discipline an artist, basically. You leave him place to express himself - if you have this place. You need to feed him with more difficult tasks, but also tasks that can afford to be late if he's not in the mood that day. Overall, at the end of the week, he'll have done far more things(and far more complex) than others. Others, though, will have done things that are time-critical.
Of course, the thing is : do you have such tasks? If not, maybe such a high potential worker is not suited to this team. If you"ve got challenging tasks, OTOH, dump them on him : he'll love them. And it's also easier for others to accept a worker with a different schedules if he's doing other tasks. It's only a partial answer to point 1, but still.