Visitor mode improvements

I think the visitor setting for multiplayer can use some improvements. The main one being that visitors can ride animals. I own a world where my friends can tour and one of them rode my donkey off a cliff, killing it. I think that should be fixed. As well I think that visitors should not be able to pick up items. In that same world players are able to collect mob drops and fallen items and, because of the way visitor is made, they cannot return the items to me