Somewhereat1l,
Crew won't have to be paid an extra 15 minutes. Why? Because on a B777, it will be an average of 8 blinds per crew member (max) to shut, whilst doing the security check. It will take an extra 90 seconds (on average) to do, so why want pay for 15mins? (By the way, I'm BA CC)
As for the risk assessment - don't even go there. Crew close (or insist on closing) blinds during the flight with passengers seated, whereas this new thing about closing the blinds will be easier due to no passengers being in the seats during the procedure. No risk assessment needed, as far as I'm concerned.