I've looked into doing the exact same thing with catless headers and my FabSpeed exhaust. Problem is, you're probably better off just buying high flow cats that fit. The cats themselves are not cheap, and once you factor in custom labor to weld them into your test pipes, you more than likely won't have saved anything and had a bunch of lost time and added frustration.
To answer your second question, yes, moving the secondary O2s to be in line after the high flow cat should eliminate the CEL and let you pass a smog test. Hypothetically, at least.
Patrick
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