WOMBAT a very bad house guest, eats roots and leaves!!
Doubt if you can domesticate a wombat,young are very engaging,but they turn feral pretty quick. BTW seen the size of wombat holes? you wouldn't want them in a garden. Also, an adult wombat can get pretty aggressive.
Why not a goat?, if your fruit trees are protected, a grazing animal will keep the grass and weeds down, plus you get some milk!!