Maybe consider 3 Captains. One would always be off duty and you rotate them when back at base. Expensive maybe, but not as expensive as having 2 crews obviously. Cabin crew, I'd say have 2 available based on the routes you have indicated. Flight frequency will determine overall crew numbers.
I'm involved with managed aircraft (UK based) so if you'd like to discuss all requirements, including engineering support, cabin crew, ops and so on and maybe look at benefits of outsourcing, I'd be happy to assist.