Wakins, jikin, and watonai are pond fish, in spite of their different tails. They can be mixed in a pond with commons, comets, and shubunkins. Here's what a leading producer (Rain Garden) has to say about fantails in ponds:
"In a sense, fantails and ribbontail are intermediate between the hardy varieties like hibuna or wakin, and the fancy varieties like oranda, telescopes or ranchu. The ribbontail, in particular, are nearly as tough as the hardy varieties and can fend for themselves with little care in a water garden or tub. They can also be mixed with hardy varieties or mixed with fancy varieties without problem."
http://www.raingarden.us/goldfish-fantail.htm
I've heard mixed reports on mixing fantails in ponds with faster fish. As for the more deformed fancies, the greater the number and severity of the deformities, the weaker the fish. They can be kept in ponds with similarly disabled fish in warm weather.