I'm not as confident talking about the genetics of crests. It seems like the gene for crests in Legbars is a single gene that is partially dominant, as a cross with only one copy (the olive eggers for ex) has a small crest, but almost always some crest, whereas the full legbar pullets have great crests, but not nearly as large as crests on polish and silkies. So, there must be multiple genes with silkie cresting. Are some dominant or partially dominant? I really don't know. There are probably answers out there, as chicken genetics are pretty well studied.
Funny how the "barnyard mixes" often create some very nice birds. I've seen some gorgeous chickens running around the farm. The problem is, how could you reproduce those neat birds? They are unique and serendipitous, but as a breeder a bit frustrating, which is the main reason that "breeders" look down on them so often. I'm always afraid someone will show me a pic and say "make me some of those" -- and I never could.
You do have some neat birds in that group. If you eventually selectively breed them for traits you like, there is no reason you could not get a fixed strain of bantams that have the qualities you value most.
