You're required to fly OWE segments on aircraft operated by the OW airline (plus in many cases its regional "offspring", e.g. BA/Comair and others), so the IB codeshare you mentioned wouldn't be allowed.

I can't speak to the seasonality question. I'm not entirely convinced that coach-cabin OWE's are the best use of one's funds - I spent much of my life flying in the cheap seats, and consolidator fares were always much cheaper than the best deals I could find on "real" airlines.