LO,
Good spot on the IOC, and you are absolutely right on the SAR content. However, in the UK, the ability to declare 'IOC' is FAR more flexible than that allowed to the US customers, where the fully independent OT&E setup calls the shots to a large extent. (Remember 'Case White' for Typhoon?)
If the UK wanted to achieve an earlier 'political' IOC for F-35B in a land based role with some form of 'undeclared' deck capability, I have no doubt that they could do that.
That said, your point is well made. I'd agree that a 'proper' IOC looks to be around 2019.
Best regards
Engines