I think he is a good player for a lower level super league side.
Personally I think that as the club has grown to aiming at regular top 8 finish and pushing towards top 4, unfortunately for Sio we have probably outgrown him. Add that in alongside Arona being higher quality and physically bigger, along with the younger talent such as Crowther and Batchelor, ultimately his chances are going to be limited.
I would expect Sio to be one of the better, stand out players at championship level with Halifax.