I know there are independent investigations, but is it possible Blackpool Police are still investigating the Downes and their associates in the shadows and that's why they have left them alone? Wishful thinking perhaps? This is a bit macabre, but most of the people associated with Downes don't drive but it wasn't long before Bonfire night...I suppose that could present an opportunity for disposal.
I'm fixated on this element of it - body disposal - because I wouldn't think any of their nonce gang drive and that part of Blackpool is so busy.
Another thing I can't help thinking of is that Bobs Ewing and Downes were at least acquaintances. When questioned about where Paige Chivers was buried, Gareth Dewhurst wouldn't say because it was "too dangerous". At that time, I thought it was because he was scared of Ewing. But now Ewing is 3 years dead so why not tell now?
Anyway, I think the key to this is looking at all of the initial suspects before the police focused on Albhatikki and Raveshi and look at who had access to a vehicle and possibly any property not associated with the Downes or their closer circle where Charlene could have been taken, alive or dead at that time.