WS continues to be profitable because their costs are so much less than AC's. If they go ahead with a second fleet type, whatever plane they choose, it will be something that maintains their cost advantage -- which means no expensive CRJs or ERJs. The 110-seat C-Series is too close in size to WS's 119-seat 737-600s to justify a separate fleet. The Q400 makes the most sense, probably something like a 74-seat version, and could be used on shorter existing routes as well as to compete with Jazz on routes that can't support a 737.