The product of BSL/RSL will produce completely scatter bred birds. Absolutely no way to predict type, color, comb or leg color even. Since what you are doing is combining two birds, each from separate and segregated male and female lines, that's four completely different sets of genetics lining up to play roulette in an egg.
First generation should lay like nobody's business even if they are weird looking.
After that - successive generations gain type if you choose for type, and lose production.
So if you shoot for a specific look in subsequent generations you lose production. If you re-isolate the best layers, and a specific roo line, you'll eventually reproduce some form of specific egg layer but getting back to either BSL or RSL will probably take awhile.