I'd like to expand on why I'd prefer the US format over civilians vs celebrities.
Firstly, I don't buy the "we already have this - so why don't you watch that instead?" argument. If Endemol themselves had used the argument of "we have Big Brother in the Netherlands - why don't you just watch that instead?", the format would never have expanded across the world in the first place.
Secondly, I think it's safe to say that anything left of the BBUK format is probably dead in the water in this point, hence why they want to make a radical change this series to make it seem like a new show.
That leads me on to my next point - these changes need to have longevity in mind. Be honest, does mixing celebrities and civilians sound like an idea that could be repeated again? If anything, it's a change that only has a quick boost in the ratings in mind and not the long term future on the show. It would probably also help bring the show one step closer to it's eventual axe and replacement with a longer Celebrity Big Brother.
Switching to the US format on the other hand seems to me like a bold move that
does have longevity in mind, as it's an actual change rather than a twist in which the novelty will wear off around 2 weeks in. Let's not forget that the whole reason why the US format was created in the first place - the ratings were abysmal and Endemol/CBS needed to make a change in order to stay on the air (aka - the situation Big Brother UK is in right now). The US format is thriving in America and in Canada, with a similar format running successfully in Brazil, so it's not like it's dying in every market that it launches in.
The basic format of strangers living in a house together being watched by the public with evictions taking place would still be there, it's just the events up to and during the eviction that would be different. Regarding the phone vote, I don't think that Channel 5 is even making that much money of that anyway, but a good way of replacing that would be a Live Feed on the website that could be offered for free with product placement and advertising opportunities split between a profit and covering the cost or on a paid subscription basis that would do the same.
The production team can still cast the same characters that we get and we can still have the nightly highlights show - it's only the game format that's changing. No-one is saying that the editing style should change either (well, other than the already existing changes that need to take place) - the producers can still use the same story-arc that focuses on the housemates interactions rather than the gametalk (which isn't as common as some might think).
Don't get me wrong, there are other options that I'd prefer to see (I've said a lot that I'd prefer that they use the BBAU 5 points/superpower system and offer both VTE and VTS), but switching to the US format wouldn't be anywhere near as bad as some are making it out to be

. The ratings were already abysmal last summer with it falling under the 1 million mark on some nights, so Channel 5 haven't really got much to lose at this point.