And they are made in resin. Not plastic.
I'd be very surprised if they departed from the existing supply system they're using for the alternate heroes.
For the OP though, while it may be a while before the "official" alternate heroes are available, there are several miniature sources from whom you might acquire your own custom pieces. Reaper Miniatures has a line of minis that includes a number of western themed figures. I think the only one I couldn't find a very good proxy for was the Nun.