Nominations and evictions are the key component of Big Brother and they remain - just in a different format. The diary room is another key component, as is being confined in the house.
Now most of us would say the show being broadcast as it happens and a 24/7 live feed are key components too, and I'd agree. Others would say the public voting is too, and I guess whilst that has gone on a weekly basis it is still there in determining the winner, so like nominations and evictions remains but in a different format.
I wonder if they'll do letters from home for the HoH - with a week in a show that is probably a waste of time, and a key component of those letters is usually people saying they're watching and you're doing well etc., so they'd be irrelevent now anyway.