While your idea of WR is a good one, and I think that's what I would choose if I had your goal in mind, For myself, I'd get some Dixie Rainbows aka Pioneer, and breed them forward. They are a hybrid meat bird, grow out to good processing size by 12 weeks, forage well. Not prone to the systemic failures of the CX. The pullets make nice layers, and they breed forward "true enough" to produce multiple generations of good meaty birds. I would not put a DR roo over a standard LF layer hen b/c of the size discrepancy. The DR are huge.