BEW to BEW will get you all BEW, if that is what you are looking for? Expanding the gene pool is "generally" not really needed, unless of course one is talking about their own personal herd and wish to get more BEW blood into their herd and don't have easy access to good BEW stock in their breed.. What a lot of BEW lack is TYPE which is obviously not a concern with pets. If you are breeding for showing,and wanted to expand your BEW into a better typed rabbit, then you would introduce good non BEW's into the gene pool.