Any good recipes for a soft but delicious buttercream frosting that can be dyed and piped on to cupcakes?

there are tons in the recipe section !!! Pull up the Frosting section and you will find plenty to try

I use mine for everything: http://forum.cakecentral.com/cake_recipe-6992-0-Indydebis-Crisco-Based-Buttercream-Icing.html

Are there BC icings that CAN'T be piped?

I am not sure but it sounds like you are looking for a noncrusting buttercream if you are wanting it to stay really soft and not crust over at all. Take a look in the recipe section. I also thought that all buttercream could be piped and colored. I have not made or used a noncrusting buttercream yet so that is about all the help I can be sorry.